History

When The Summer Sun Celebration was complete, and everypony was leaving, Twilight needed to ask Celestia something.

"Celestia?" she could barely say the name, after all the things she's seen.

"Yes, Twilight? Is there something you need?" Celestia said.

"Can I... talk to you in private?"

Celestia frowned. "Of course."

Later, Celestia met Twilight in her guest room. Twilight needed to pack up to head back to Ponyville, so they thought the room Twilight stayed in would be a good place to talk.

"Is something wrong, Twilight?" Celestia said worriedly.

"...Yes, I guess there is... it's about... well.... History, I guess..."

"Oh dear... did you find out somehow?" Celestia said. She didn't sound like she did in the past. If she did, she probably would have yelled at her, demanding she told her how she found out. Instead, Celestia only seemed sad.

"Yes. If we're talking about the same thing. Nightmare Moon, and all of that?"

"Yes, we are. I need to tell you something, Twilight. Please believe me when I say I'm not lying as I talk to you now."

"Ok..." Twilight said.

"This was simply because of greed, and a grudge." Celestia said sadly. "Long ago, my father died against an enemy. I still don't know the enemy's name today. My mother was bleeding out, though we had defeated the enemy, Sunbright, my mother, had been injured, and wouldn't be able to heal without a strong alicorn magic. As you have probably learned, I do not raise and set the sun. I can't even do it with the moon. I am weak. My sister, Luna, however, had the strength to heal her... and she didn't."

"She didn't? Why?"

"She said that her reason for not healing her, was that she had lived for a bit less than a million years, and anypony who has lived that long deserves to end eventually." Celestia then said sadly. "I didn't understand. I hated her from then on. I understand now, and I shall say it simply... Over a thousand years. Over a thousand years, and I have eaten every sweet, seen every new technology and magic, I lived long enough to greet Starswirl the Bearded and then live another thousand years. What do I do now..."

Twilight thought about it. She understood quickly. "She was getting tired of... life?"

"Yes. I thought Luna just wanted to watch her mother bleed and die, because she deserved it for something she may have done in the past. I was using the word 'deserved' wrong. She deserved to not be bored, and confused, with nothing left to do..."

Twilight instantly felt bad, though she couldn't tell if this was another lie. "What happened next?"

"I think you saw. Greed. Somepony thought I could raise the sun, and I was met with compliments and joy from everypony who saw me. I grew greedy, and didn't want the compliments to go away. I thought Luna would steal my popularity, and so I hated her even more... Then, Nightmare Moon... I'm sure you know what happened next?"

"She came back, and we turned her back to Luna, and... you weren't mean to her..?"

"I understood, and felt bad for my mistakes. We apologized to eachother, and promised that it wouldn't happen again. I knew we needed to apologize when she came back from the moon, because after I banished her, instead of feeling better, days in the castle got... lonely. Gloomy. Even with the guards and servants to talk to, I felt like somepony was missing. I realized what it was. I had no more family members living with me."

Twilight felt sad at the tale. "Oh... how do I know you're not lying again?"

"Because you can ask me." said Luna from behind them. "Sorry for eavesdropping, but I'm sure you can trust me, Twilight Sparkle."

They all hugged, and tried to pretend this never happened.