I have heard ponies say that living so long would be a curse. That it is a burden. That it can break a pony's mind. There is some truth to that, but it's not the whole truth.
Ant Mill is a college student, stuck in a dead-end internship she took just to fulfill her requirements. All she does is wish she was somewhere else, but when she has a chance encounter with the Princess of Friendship herself, all that changes.
"When I read their letters... I think about how temporary everything really is." A lonely princess pores over her studies in a frigid castle, desiring nothing more than the warmth of an old friend.
Celestia reunites with her former student over tea after a forty-year vacation spanning the world, only to find that Twilight has changed quite a bit more than she expected.
Over the past few centuries, one of the only constants in Princess Twilight Sparkle's life is her friendship with Discord. There is absolutely no way their relationship will ever change.
There are few constants in nature as universal as the fact that the big spoon will always be big, and the small spoon, small. However, what happens when your tiny unicorn marefriend becomes a princess and is suddenly four heads taller than you?