He also seems to be pretty screwed up.
I know /a/ will say I'm stupid for thinking this, but during the Lucci/Bueno fights Luffy said the same thing, that he had to become stronger in order to protect his weaker friends from all the bad shit coming at them. He knows the gears are breaking down his body and slowly killing him, but he's only concerned about smiling, food, and sailing with friends. He's afraid to be alone you see, like anon, so what he does to protect his relationships is to fight, and fight to the death. He can't really trust people so he puts his life on the line for them so that they might feel indebted to him. I noticed this was especially clear during the time Ussop wanted to ditch Luffy back on Water 7, and Luffy felt that he was losing 'another' friend.
In reality, Luffy is an insane, scared little child that throws himself into battle in order to feel anything. This also explains why he feels nothing towards Nami besides platonic love.
He's a sociopath.>>12179731