Celestia raises the sun that morning with a giant grin on her face, with a lightness inside her chest that threatens to choke her up. Celestia cancels all her meetings for that day and evening, and makes sure that the castle is bustling with activity, preparing and working constantly. Then she walks to the end of the hall, to her grand room, while everything comes to boil to the surface and she's forced to blink back tears. She opens that door with a careful expression-- one that folds and explodes when she sees what's inside.
Luna is still there.
Worn and tired, maybe slightly terrified, but there. Laying on her bed, curled up and sound asleep. Finally, after a thousand years, Luna has returned to her.
Celestia chokes back a bittersweet sob. Finally.