Conversations were had and forgotten, promises were made and forgotten. But Applejack and Rara made one promise that held true; true friendship never ends.
Nopony should bottle up their feelings. Sometimes, all a pony needs to do is talk with their friends. Sometimes, all a pony needs to do is pretend someone's listening. So, Diamond Tiara hides in her room, writing away her troubles with letters.
Luna was never banished, Discord is Celestia's court jester, the Elements of Harmony do not exist, and Twilight grows more pompous and more egotistical every day. Celestia is not amused.