I come from the belief that characters should fail. I don't mean just "they should have to work for their victories," I mean if they don't experience a loss and figure out how to live with it going forward, there's a very fundamental part of them that's never explored.

Not exploring that part of them is also perfectly valid. Not every story needs to be like that. And how it happens is up to you. But loss, failure, losing and sometimes just things not working out are huge parts of being human. They're worth looking at.

Then again, I do watch a lot of anime. So maybe I just like seeing heroes clench their teeth and punch the ground while thinking about their friends.