"Oh look, there's the sun! Time for me to turn in!"
Celestia scowled as her sister fled the balcony, vanishing among the spires of Canterlot Castle. Perfect, now I get to spend today cleaning up the mess she left? Celestia sighed. Luna, I love you, but you're not making this any easier for me. She shook herself, clearing her thoughts in preparation for the day ahead. Well, Luna did my job after a full night's work. Guess it's my turn. Her horn lit up, its aura once more a familiar yellow. After all, the sun isn't going to raise itself.
The Princess of the Day put forth her power, and Canterlot was soon greeted with a magnificent sunrise.
If the sunrise that day had been particularly spectacular, the sunset that followed was decidedly less so. Rather than slowly sinking to the horizon in a shimmering blaze of color and glory, the sun descended with little fanfare, its disappearance far overshadowed by a glorious moonrise. And while most ponies were content to enjoy Luna's masterful work that evening, some couldn't help but wonder what could be ailing Celestia to put so little care into her daily task.
Some ponies, however, had no need to speculate. Every pony in Canterlot Castle knew exactly what the problem was. Their beloved princess had had a bad day.
To say that Celestia's day had been trying would be an exercise in understatement. Her earlier fears aside, fixing Luna's missteps from the previous day had actually been the least of her trials. The foals' field trip was easily funded, the crown having no shortage of bits, and the foals were quick to forgive. The timberwolf issue had been somewhat more of a project - honestly, how did those creatures end up so far from the Everfree? - but having lived in that accursed forest a thousand years ago, Celestia was accustomed to dealing with far worse; the townsponies near the White Tail Woods, however, were understandably quite shaken, and it would be some time before their fears were fully assuaged.
But Celestia would sooner have faced a thousand timberwolves with her wings tied than endure what followed upon her return to Canterlot.
Whatever else one might say about the elite ponies of Canterlot, they were certainly observant. Some had gossiped among themselves for weeks regarding the mounting tension between the Royal Sisters, and Starlight Glimmer's arrival had not passed unnoticed. When Princess Luna appeared in her sister's role the previous morning, sitting on her sister's throne, with her sister's mark upon her flanks, nobles, guards, and servants alike were quick to make the obvious connection. For twenty-four hours, gossip and speculation ran wild throughout the city, each individual coming to their own conclusions as to why this was happening. Unfortunately, a few of the more paranoid nobles, including Prince Blueblood, had come to the conclusion that this was a plot by Luna and/or Starlight, depending on whom you asked, to overthrow and replace Celestia. Cooler heads, Fancy Pants high among them, rightly condemned such theories as utterly implausible. But, as any longtime resident of Ponyville could tell you, when one small group of ponies starts to panic, others are quick to follow.
While afternoon court was not always a pleasant experience for Celestia, at least it usually ended with some progress having been made, some new project approved, some dispute between nobles resolved. Today, however, was different. Convincing nobleponies of anything could be difficult at the best of times, but when they were in a state of panic and actively expecting, or plotting, a coup, the task became monumentally more implausible. One might as well try to convince Pinkie Pie to go on a diet. Fortunately, nopony was bold, or foolish, enough to directly accuse Luna of treason in front of her sister.
Nopony, that is, except for Prince Blueblood.
Blueblood had always been wary of Luna. Like most ponies, he grew up hearing the tales of Nightmare Moon, a monster who would gobble up little ponies unless she was sated with sugary treats. However, Blueblood knew more than most about the origin of those foalhood tales, and he was by no means stupid. When the Summer Sun Celebration in Ponyville was interrupted by the legend herself, and then Celestia's long-lost sister just happened to show up the next day, Blueblood wasn't the only pony to make the connection. Like most of the other nobles, he noticed the sisters growing more distant, and when the darker alicorn took his aunt's place for the day, his suspicion became certainty.
Now, Blueblood was not tactless; far from it. He was normally more than capable of reading a pony's tone of voice and body language, and he had the highest respect for his beloved aunt. But as the two sisters had so succinctly proven to Starlight the previous morning, sufficient stress and the heat of the moment can cause anypony to say or do things they normally wouldn't. And so, as tempers ran high among the gathered nobles and Celestia strove in vain to regain control of the room, Blueblood opened his mouth and inserted all four of his hooves, calling out loudly for vengeance against both the former creature of nightmares and the pony who had assisted in her attempted conquest.
The deafening silence that followed told Blueblood one thing: he had badly overstepped. Patient and kind though his aunt was, unknown to him, she had been teetering at the edge of sanity for the past hour. Hearing such accusations and demands from her adopted nephew was the last straw -- and Princess Celestia's legendary composure finally snapped.
The temperature in the room noticeably increased. Sweat trickled down everypony's faces, from both the sudden heat and sheer terror they felt as they stared at their benevolent princess. Her rigid mask of motherly calm was gone, her teeth showing beneath curled lips; her left eye twitched violently, a dangerous light flickering in her slitted pupils; small tongues of orange flame danced at the edges of her ethereal mane. Nopony dared to move or speak, lest they unwittingly draw her wrath upon them instead.
It lasted but a moment, and then the heat was gone, the mask firmly back in place; Celestia, kind, motherly, infinitely patient Celestia, sat upon her throne, the usual gentle smile upon her lips. The petrified nobles aside, it was as if nothing unusual had happened -- and yet, every noble, guard, and servant in the room knew they would never be able to erase that snarling visage from their mind, a stark reminder of the true power their princess wielded.
As for Celestia herself, she was puzzled at the sudden quiet. One moment, a hundred panicked voices were shouting over each other demanding answers or retribution; an instant later, every eye in the room was fixated on her, knees trembling, jaws hanging, terror in their eyes as if she had ordered their execution!
Dismissing this mystery for the moment, Celestia seized the opportunity the silence had provided and cleared her throat. "My ponies, I understand that the events of yesterday have given you cause for concern, but I tell you once again that your concern is unmerited. Since I seem to have your attention now, please listen carefully, as this will be my final word on the subject." She then proceeded to recount the events of the previous day in full, being careful to emphasize the difficulties that each sister encountered in doing the other's job, from Luna's strained smile to Starlight's nightmare. She spoke of the fear and uncertainty she felt facing her evil self in the dream, her reconciliation with Luna, and her sister's reassurance that ultimately helped her to defeat the nightmares. She explained Starlight's abilities and her role, both as Princess Twilight's former student and as the pony who ultimately brought the two sisters closer to each other than ever before.
"In the end," Celestia concluded, "I am grateful for Starlight Glimmer's actions yesterday. Thanks to her, both my sister and I now have a better understanding of and appreciation for each other. The experience has taught both of us an important lesson, one that I hope you yourselves will take to heart. As this is my final word on the topic of yesterday's events, I am considering the issue closed. If there are any more issues that require my attention today, please bring them forward now."
Never again, Celestia thought as she plodded wearily to her bedchamber, I am never pulling a double shift again. Oh sister, is this what you had to endure yesterday? I am so, so sorry for putting you through that. Her eyes narrowed, though whether from irritation or exhaustion was difficult to tell. Next time I can't sleep at night, I am canceling my morning appointments and sleeping in, hang the nobles. She barely had the energy to greet her sister as she passed by, the thought of her warm, soft bed consuming her full attention. She didn't even bother to stifle her yawns as she reached her goal.
At least, she thought as she nuzzled into her pillow, it's finally over.