Don't make me do this, Luna.
"Go ahead! Blast me with the Elements! It will do no good! I have power over--" A flash of light shone blindingly, and a horrid scream could be heard throughout Equestria. The light faded into twinkles that fell down to earth before dissipating into nothing. The victorious alicorn landed on the stone floor of the castle's throne room with a small, graceful "clop". The battle was over.
Evil and darkness had lost this night to justice and light. Celestia had defeated Nightmare Moon, the vile and evil would-be ruler of Equestria and bringer of eternal night over the whole land. Celestia, Princess of the Sun and Keeper of the Day in Equestria had vanquished this threatening foe.
Unfortunately... she had also banished her only beloved sister, Princess Luna, Daughter of the Moon, Keeper of the Night, to the dim, silver moon overlooking the world. Now, there was an everlasting mark on the moon, perhaps a grouping of craters, that formed the image of the head of a regal pony-- Luna. Celestia's sister.
The princess fell to the stone floor, and wept tears of great sorrow. It was all she could do, considering the great exhaust that filled her body, mind and soul. She was too tired to rise-- unmotivated. Luna was gone. Celestia's only family was now trapped in the one object that ruled that which she loved most-- the night. Sighing, the ivory princess pushed away her multi-colored mane out of her eyes-- multi-colored mane? Celestia saw the streaks of emerald and sapphire among the rose-quartz color her mane usually solely obtained. What had happened?
But then Celestia noticed something else missing from the room. The elements. Had they, somehow, someway... come into her? Her mane? A beautiful change--
--and Luna wasn't here to see it.
After a few more moments of relentless sobbing, Celestia finally regained the strength to physically stand on her own four hooves. But her heart was still in the depths of despair. The princess slowly walked out of the destroyed throne room and up to her bedchambers. When she'd arrived in her room, she climbed onto her bed, buried her head in her feather pillow, and just lay there. Tears were still falling from her eyes, but the sobbing had stopped.
There was no hope left. Eternal night had been prevented, of course, but even more had been lost than protected; the second half of the monarchy in Equestria was gone forever, trapped inside a sphere of grey, dull rock. Celestia was a born leader, strong and able, but Luna was the thing that held Equestria together. She genuinely cared for the people, and often visited their dreams at night, especially the foals'. Now when the young fillies and colts had nightmares, no pony would be there to protect them from the ghouls and goblins. Their defender was lost.
Celestia, finally tired of the silence that filled the room, shouted angrily and desperately, and to nopony in particular, "What am I going to do now?!" She looked up to the bright silver moon, and bellowed at the silhouette of a pony that was engraved upon it, reminding the Sun Princess of what she had done just hours ago, "You were their light! You were always there for them! I was just a stand-in for political matters-- you were the real ruler! You cared about your subjects, and I stood behind and watched!" The ivory alicorn cried after pausing to take a breath, "I should be up there, not you!" After another pause, a last desperate scream pierced through the night. "LUNA!"
The princess sobbed and sobbed, feeling remorse and anger simultaneously, alone in the dark. But suddenly, she felt a touch on her shoulder. Startled, she jumped up and turned to see who had touched her. "Who..." But she saw no pony. But she did hear a voice.
Celestia.
"Wh-what?" the pony looked around the room, trying to see the visitor. "Who's there?"
I have heard your cries, Celestia. And I have come to give you comfort.
It was a gentle voice, firm, but calm. Celestia tilted her head in confusion. "I don't even know who you are!"
I Am.
"You are who--" Then Celestia remembered. She did know who this visitor was. She hadn't heard from him in a long time. "I... haven't... heard you in..."
I was always there, Celestia. The voice grew sad. But you refused to listen when I spoke.
Celestia shook her head fervently. "No, no. I have always heard you when you spoke."
I know you heard.
A moment of silence fell in the room. But Celestia broke it softly. "But I never listened." The pony hung her head. "I only listened to myself after Luna and I came to power." Luna. Celestia felt tears in her eyes.
You miss here dearly.
"I do."
Celestia, I will always be here for you. All you have to do is listen for My Voice.
Celestia saw nothing, but she felt an embrace around her, and she accepted, whispering, "Thank you." She closed her eyes and smiled.
***
"Princess!" Celestia opened her eyes. She was on lying on her stomach on her bed. A guard was at the door.
"Y-yes?"
The soldier said, "Er, pardon, but do you think it may be time to raise the sun?"
Celestia checked the clock on her wall. "Oh my--!"
The sun was quickly raised in the sky, and ponies all around awakened just in time to see the late morning light. The guard that had awakened earlier her nervously said, shaking a bit, "I'm not sure if I should say this, but I heard you last night... You were weeping horribly. I wanted to come in, and was about to, but then you suddenly stopped. What happened, Your Highness?"
Celestia smiled a bit. "I was visited by an old friend."
The soldier was confused, but the Princess seemed calm, so this most likely wasn't an intrusion. He simply answered, "Ah. I see."
For a thousand years, Celestia raised and lowered the sun and moon, saddened that her sister was no longer with her, but she always had peace, for she no longer listened to what her own voice told her to do.
She listened to the advice of the Voice that had come to her in her darkest moment in the middle of the night. And she always found comfort in his embrace.