While students might joke that Independent Study with the Princess was an easy alternative to real classes, they were fools. Sunset knew that and never bothered to correct them. It would be a waste of her time to educate idiots - that's what the teachers were for.
Yes, it provided Sunset considerable leeway - many of her tasks could be accomplished when she felt she needed to rather than in a highly regimented schedule. What she was doing minute to minute mattered less than her end results and to the average student that seemed like unlimited freedom.
It also afforded Sunset opportunities others would never get, like the experiment she was performing now: leaning over a triangle of carefully prepared rubies on a heavily warded table in the annex of Princess Celestia's personal library, pouring magical power into creating a miniature sun.
What the complainers didn't usually recognize was the level of expectation that her 'privilege' put on Sunset. Those end results did matter and she regularly had the Princess looking over her shoulder to see how things were going. That was another thing that the average student would think was a help and an honor - because they'd never had to deal with it.
"Your containment rune is too close to the edge." Princess Celestia pointed it out in what she likely meant as a helpful tip, but as usual came out as a half-sneer.
The fact that the Princess was probably trying to help didn't. Sunset ground her teeth harder. "I know."
"It's going to backfire soon," Celestia stated, more pointedly this time.
"I know."
"If you know, why aren't you doing anything to correct for it?"
That pushed Sunset over the edge. Her head twisted to glare at the Princess - and she lost concentration. The spell fizzled with a dramatic flash and muffled kaboom. The three carefully prepared rubies absorbed the uncontrolled energy and were cooked from the inside out, transforming them into lumps of molten carbon. Sunset, in turn, released her rage by kicking the nearest object: a wooden lectern. It fell over, dropping the centuries-old spellbook they had been using to the floor where the already fragile bindings crumbled and spilled it into a mess of pages.
Several beats of silence passed before Princess Celestia calmly asked, "So what was your reason for not correcting it?"
Sunset wanted to be angry. But experience told her that wouldn't help anything and wouldn't stop the Princess from asking that same question until she got an answer. "I didn't notice it was out of position until after the spell started," she stated through grit teeth. "At that point I couldn't move it without disrupting the entire spell matrix. I could have just reinforced the shield on that side if somepony had let me concentrate."
"Not every situation where you need to concentrate will be a perfect environment, Sunset. You need to be able to ignore disruptions. If my asking what you were doing was enough to break your concentration, then it speaks poorly of how you would handle larger or louder problems." The Princess clicked her tongue, scolding her student. "I'm disappointed. You need to be better prepared."
Sunset snorted. "I need better concentration to be a princess? Is that what I need to finally be ready?"
The P-word made Celestia frown deeply. "Yes, in fact, that's part of it."
Sunset's ears perked up at the unexpected admission to what she had meant as a rhetorical question.
Sighing, Princess Celestia stepped away from the wreckage of the experiment and back towards her personal library. It was a relatively compact room - Celestia only kept a small number of books for herself rather than in the greater Canterlot Library - but it was far brighter than one would expect for a library, with massive stained glass windows interspersed with gilt bookshelves and overstuffed plush couches. "Your temper is a factor, Sunset Shimmer. To be a princess is to be beyond such things. You cannot allow yourself to be affected by emotions and base passions as all of ponykind's fate rests on your withers." She lit her horn, picking up the now-scattered pages of the destroyed spellbook and gently sorting them into a pile on an end table. "Becoming swept up in anger or losing focus is unacceptable when the price isn't paid in focusing gems or a few minutes of frustration - it is paid in lives." She turned, looking to Sunset with an inscrutable smile. "You've never understood that to be the Princess, you cannot be a pony. You must set aside your desires and feelings to make the best possible choices."
Perhaps Princess Celestia expected humility or understanding as a response. Instead, she got a sneer. "Cadance isn't like that."
Celestia's smile turned sour. "She is young still."
Taking a step closer, Sunset defiantly glared upwards at the Princess. "And I thought you approved of her and me. That doesn't sound like her ignoring her emotions."
Celestia turned away, walking slowly past the shelves. "Let her enjoy her youth. There are many years for her to learn these lessons in."
A flash - and Sunset teleported in front of Celestia, jaw set and once more preparing for a fight. "What, I'm just something to entertain her until I die and she moves on to the real princess stuff?"
There were no words, but they weren't needed. Princess Celestia's forlorn, regretful expression said 'yes' far stronger than any speech could. Sunset rocked backwards, struck by the raw force of Celestia's pity.
The Princess walked around Sunset, moving languidly towards a clear window between two of stained glass. (The left showed a stylized conference atop a mountain between Celestia and a massive dragon; the right, a similarly abstract scene with a group of griffons bowing to her.) She said nothing as she passed by the lunch that had been set out for them - two salads (apple, walnut, and cranberry), tea (silver needle white), and a light dessert (slices of roast pear in honey). A cranberry floated out of the salad and into her mouth as she gazed out at Canterlot below.
Recovering herself, Sunset stomped after her, frustrated anger mixing with stubborn defiance. "So that's it? You're never making me an alicorn so I'm just a plaything for the rest of my life?"
"You are not ready to be an alicorn," Celestia sighed for the seven hundred and thirty-third time. "Perhaps you will be some day, but it is not my choice to make."
"And just what do I need to do to be ready? You're always so damn vague!" Sunset tried to get in Celestia's face again, but the basic physics of the Princess facing the window prevented it. "Even if you don't care about me, you care about Cadance. You should want me to stick around for her sake!"
Another sigh - heavy with centuries. "It would be better for her if you did not."
Again, Sunset staggered as the words slapped her. But this time she was more ready and recovered faster. "So you want the Princess of Love to shut herself off from emotion?" She snarled, teeth bared and dangerously close to that long, swan-like neck. "You can't be that dumb."
She obviously had a point, because Celestia didn't answer immediately. Instead, after a pause, she changed the conversation. "You are not a plaything, Sunset Shimmer. You are a thinking, feeling being with a mind all your own and amazing dreams. I have met very few ponies of your caliber, and you are closer to me than any other in living memory." Her eyes flicked to her student's. "I will miss you deeply when you are gone."
Sunset winced.
"That is the nature of an alicorn. Being eternal in a mortal world weighs heavily on the soul. No pony can survive completely isolated, but an alicorn has no one to anchor to. We are alone in eternity." There was a tremble in Celestia's limbs - a tense shaking, like she was braced on the edge of a cliff and staring down the distant fall. "I've said before that I have to protect you from being a princess. This is an aspect of it. You are my brilliant student, Sunset Shimmer, and I don't want to see that extinguished."
Anger flickered in Sunset's heart again. "So you think I'm too weak to cut it?"
Silence was her response. Long seconds of silence as Princess Celestia stared out at her city and her nation. "You don't understand," she finally said with quiet resignation.
"So explain it to me." Sunset's words came out as almost a threat.
And the Princess sighed heavily.
Her magic reached out to pull closed a heavy set of drapes - and in the same moment, so did every other pair in the library. Each of the fleet of windows was closed off, shutting out the exterior light and leaving them both in twilit shadow. "You are a pony," she began as she walked away from Sunset, moving towards the center of the room. Celestia's voice was steady and flat - bedrock. "To be a princess is to give that up. To have a life that is no longer your own. Every word, every action - even those you think are not observed - must be chosen with thoughtful care. You understand the power of a princess' words, but not the reason." The room's shadows were pushed back as Celestia started to glow. Not her horn or her magic, but her. "The mistake you and so many others make is that you believe Equestria serves its Princess. Some get closer, saying it's the other way around, and the Princess serves Equestria." The glow intensified - candle to lantern to bonfire. Sunset was forced to squint as Princess Celestia became to bright to look at directly. "The truth is that I am not Princess Celestia. I am Equestria. I am the Sun. And my life is not mine to live - it is to ensure Equestria serves her ponies."
Celestia stood triumphant - regal - glowing. Not like the sun but as the Sun. Everything else in the room was blanked out, washed clean by the power and radiance she projected almost as intensely as the force of her personality.
Then another glow pushed back. Fire burned as a barely contained reaction of magic and science ignited the air between the pony and the Princess. Without wards, without preparations, Sunset Shimmer recast her spell and recreated the Sun in miniature between them.
A panicked Celestia whirled around and reached out with her magic, dimming as she redirected her power to contain the blaze - just as Sunset knew she would. And with no need to worry herself over control, Sunset poured every ounce of magic she could into feeding her sun.
"Sunset! What are you--"
"YOU'RE WRONG." The little unicorn shouted over the roar of the star. "And even if you're right, you aren't about her! You may be the Princess and Equestria and the Sun, but Cadance is Love! You declared her that yourself!" She tried to glare at Celestia, but the brightness between them was too much. All she could do was pinch her eyes tight and try not to go blind. "She might be a princess but she doesn't have to live her life the way you live yours! And I won't either!"
"Sunset, stop--"
But Sunset didn't listen. "You're always so damn sure that your way is the only way! You're always so sure you're right!" Celestia's grip on the fireball slackened a little when Sunset said that, letting a bit of scorching heat leak free. White marble was raked by flame, leaving a sooty slash across the floor. "Cadance is going to prove you wrong, then I'm going to prove you wrong once I'm a princess too!"
"Sunset Shimmer!"
"AND YOU CAN'T STOP ME."
Princess Celestia's magic stopped trying to contain the small sun and instead crushed in on it. Like a pair of hooves clapping together, her magic compressed inwards with overwhelming force. Sunset's little sun briefly deformed against the golden magic before being snuffed out. The power backwashed - sending out a shockwave of air, heat, and sound that threw papers around and blew most of the drapes open - and backlashed - sending Sunset Shimmer sprawling on the floor with a stinging vibration that went all the way down her horn, through her brain and into her spine.
It took nearly a minute for the ringing echo to fade from their ears, and another one for the scattered pages to settle to the floor. Amidst the sound of fluttering paper, Princess Celestia carefully crossed the space and tried to help her student up.
Sunset ignored her hoof, choosing to wobble up on her own.
They exchanged looks for some time - one defiant (and squinting against lingering afterimages), one pitying - before Celestia broke the silence. "I want you to have a long and happy life, Sunset Shimmer. I wish Cadance could have one as well, but we do not choose the direction that Harmony moves in. We simply bear the consequences of it."
"You're wrong," Sunset spat, not giving ground.
And Princess Celestia hung her head. "I have been wrong before. But I do not think I am now." A heavy sigh - and her head rose up again. "Take the rest of the day for yourself, my brilliant student. That was quite a powerful display and I expect you need some time to recover." She paused before - with a slight glimmer in her eye - added, "And that includes fencing practice."
It had probably been meant as a joke. Deep down, Sunset knew that. But she still glared venom at the Princess. "You're wrong," she repeated, throat raw and voice weak.
"I wish I was." And the Princess smiled a sad, patronizing smile.