Aang hit his when he realized everybody he knew, died. He went crazy and probably would have died without Katara. Korra hit hers when she was about to kill herself. Why are their lowest points when they're about to kill themselves?
I don't understand why people think Korra loving Mako and their relationship takes anything away from her badassery, Aang liked Katara for the entirety of A:TLA and we didn't think he was any less capable of saving the world.