Forgiveness and letting go of the past in ATLA and LOK.
Katara: But I didn’t forgive. I’ll never forgive him. But I am ready to forgive [Zuko].
Asami: I’m not sure I’ll ever be able to forgive [my father], but that doesn’t mean I shouldn’t try.
Korra: [I wont ever forget what Zaheer did to me], but I am finally able to accept what happened and I think that’s going to make me stronger.