ABSOLUTELY-- that said I'm also very much a supporter of Anti-supermanism. When there's a giant fight, and your character skates out with a few scratches-- that's a huge problem to me, as well as going through something emotionally troubling and being a-okay. There are a few things that grow your character and misery is the more permanent of those things. Happiness can only temporarily visit a person and light up their personality, but that feeling will leave without leaving a lasting effect because human mentality only creates memories of things NOT to do again, and that comes from bad experiences. That said, I keep it a believable level, I don't go hay-crazay with it, moderation and balance it and it can really progress a character.