For Twilight, the increased lifespan that came with princesshood had forced her to outlive her friends, but thanks to Rarity, she will learn that centuries could be lived in but a single day.
Rarity has found a new hobby in meditating with Fluttershy, and through months of practice, she's not only learned how to listen to nature, but also how to read ponies and the inner feelings they hide. But she never wanted to read her best friend.
Sunset Shimmer invites Twilight over to spend the night at her home in the wake of the Friendship Games fiasco, and Twilight learns that they have a lot more in common than she expected.
After an encounter with a hated rival during a festival she'd been looking forwards to all year, Rarity learns that sometimes her anger blinds her to what - or rather, who - is most important.
After the battle of the bands, Twilight has something on her mind regarding the Dazzlings. Sunset has also had some things on her mind regarding Twilight.