This is how it feels to be Princess Luna right now.
It was the night before the "Grand Galloping Gala" as her sister called it. Tia had invited all the snobs which inhabited the city of Canterlot, her student, Twilight Sparkle, and the other element bearers, and had hired a band which, according to rumour, she had ‘rescued’ from Manehattan. Luna had declined every invitation to join. She was out of practice with raising the moon and guarding everypony’s dreams. What good was she as a princess if she could not fulfil her duties? But ever since she returned, Celestia did not seem to care for that. Behind closed doors, Celestia had been smothering her with affection.
Luna felt joy and relief, but also confusion. It had been a thousand years. Surely Tia had had other students before Twilight Sparkle, plenty of company? More than she had had on the moon, anyway. She had tried not to count Nightmare Moon, the lying shadow that had destroyed her life, as ‘company’, but that was easier said than done. Now she stood in the ethereal realm, lined with doors on each side, each one leading in the dreams of everypony in Equestria. Celestia had specifically told Luna to leave the door which lead to her dreams alone until she was back in practice. Being the Princess of the Night, that had taken less time than expected. That combined with the warning, made Luna even more curious, and perhaps a bit afraid.
The door opened, light flashed, and then everything went black. Luna felt like she was in someone else’s body. As the events played out, she heard a voice describing them. Bored and condescending like a play being rehearsed for the thousandth time…
--
This is how it feels to be Princess Celestia forever.
The first light brings pain. The moonlight burns you. It will always burn you. Part of you will always be flying for your life, dodging magic blasts beneath the pale moonlight as your home crumbles around you. You can hear yourself breathing. It comes hard and ragged, and it scrapes nerves already raw, but you can't slow it down.
"Princess? Celestia, can you hear me?"
You can't. Not in the way you once did. It is the voice of your old friend, Starswirl the Bearded, filled with fear, and concern, not for a friend, but for a ruler. You open your bleary eyes. The castle is in ruins. Ceilings broken, rubble strewn everywhere, windows shattered, tapestries torn, and the Elements of Harmony scattered in a circle around you. Slowly, the memories return. But it couldn’t be real. Surely it was just a bad dream. It had to be.
"Yes, Starswirl. Where is Luna? Is she safe? Is she alright?" you try to say, but another voice emerges, hysterical, with none of the practised and polished elegance that came with being a princess.
"Starswirl? Luna! Where are you? Are you alright?"
“I’m sorry, Princess, but… I saw the two of you in the sky. A saw a blast of rainbow – the Elements of Harmony – heading towards Luna, or whatever that thing you were facing was. It screamed and disappeared, and, well, see for yourself.”
Starswirl gestured upwards. You look up. Sure enough, on one side of the moon is a shadow – a hideous mocking silhouette of an alicorn. This burns hotter than the magic blast had.
“You were struck in the chest by a powerful magic blast,” Starswirl said, trying to change the subject. “There doesn’t seem to be much surface damage, but how does it feel?”
He reaches out his hoof to offer support, but you bat it away with a bit more force than you had intended. Starswirl flinches in pain and slowly backs away as you rise, but you don’t care. You don’t care how it feels. All you care about now is getting your sister back.
"No, I couldn’t have! Luna, come back! LUNA!!!"
You loved her. You will always love her. You could never will her away. But you remember... everything. You remember Nightmare Moon, the dragon that consumed your sister, which you brought the Elements of Harmony forth to slay. You remember the clash inside you, between the cold venom of your fear and the black hatred of blasting the dragon to silence her lying mouth. And there is a brief blazing moment in which you realise that there was no dragon, that there were no Elements of Harmony. There was only her and you.
You did it. You banished her. You banished her because, finally, when you could have saved her, when you could have listened to her, when you could have been thinking about her, you were thinking about yourself. It is in this blazing moment that you finally understand the trap of power, the final cruelty of leadership. Because now yourself is all you will ever have.
And you rage and scream and reach out with your magic to rip the shadow from the moon and bring your sister into your loving embrace. But the Elements of Harmony have a will of their own. To them, you are so much less now than what you were. You have disregarded their lessons. You are like a painter gone blind, a composer gone deaf. You can remember where the power was, but the power you can touch is only a memory. And so with all your fury, it is only stained-glass windows and the floor beneath your hooves that shatter, and the moon dips over the horizon, bringing forth the light of a new day. Exhausted, you lower your head and collapse, tears streaming down your cheeks.
“Please, Lulu,” you say, sobbing between breaths. “Please come back. I’m so sorry. I love you.”
For years – decades – you keep trying. But every day, morning and evening, the cycle repeats itself, and in the end, you cannot touch the shadow. In the end, you don't even want to. In the end, the shadow is all you have left of your sister. Because the shadow understands you, forgives you, gathers you unto itself. And every day, under the warmth of your sun, inside the furnace of your room in your new castle, within your own heart, you burn in your own flame.
This is how it feels to be Princess Celestia forever.
--
Luna emerged from the dream back into the hallway. She was speechless. This is what Celestia had been showing to herself for a thousand years? Celestia had been as lonely as she had been on the moon. She had never told anypony what she really felt, and they couldn’t have felt it anyway through all the masks she wore. What other demons did her sister have in her closet?
Tia may have detected her snooping around, but Luna did not care. The next day, as soon as she got the chance, the two of them would discuss this, not as princesses but as sisters. There would be no more masks between them.
This is how it feels to be Princess Luna right now.