"Sister are you okay?" Luna walks in and sees her sister struggling in her sleep, she then notes that Discord is on the side of the room. "DIS-" She starts. "Shh, your sister is retrieving an old memory." Discord quests her. "What do you- oh." Luna's eyes glow.
"Sister, all I ask is one extra hour or two for the night, please?" A little Luna whimpers up to her older sister. "No! We have already discussed this, an extra hour of night and the farmers would not be able to harvest their crops properly! Now if you'll excuse me, my advisor is present, and we have actual important matters to discuss." Celestia replies strictly. Knowing she can't win this fight Luna runs away sobbing. "On more hour, just one more!" Big Luna who has been watching the whole time moves and follows her younger self.
Little Luna cries in her bedroom for the rest of the day. "Just, hic, one, hic, more." Luna sobs into her pillow. Suddenly her head snaps up. "If she won't give it to me, then I'll just have to take it. I know for a fact that she has a magic transferring spell somewhere in her spell books, yeah I'll just take it, hehehe..."
That night, "Aha!" Little Luna stumbles upon the spell book. She walks to Celestia's room. "I knew you would try that so I came prepared." Celestia holds up a little vile. As Luna casts the spell she drinks it. Luna starts to glow... she feels a slow ducking feeling at her horn. "What no!" "Now sister I can raise the sun and moon. For this act of treason you are banished from Equestria!" Luna collapses to the floor, but instead of it disappearing it turns black. "There can only be one princess." Luna mutters as she leaves, Celestia follows but when she gets to the throne room she meets an unexpected suprise, "There can only be one Princess in Equestria and that Princess WILL BE ME!"
Luna snaps out of her trance. "Have fun?" Discord asks. Luna walks over to her sister. "My sister I have already forgiven you, I just wish you would forgive yourself"
Celestia whispers, "If I had made different choices."