One reason why he's doing this is because he hates himself.In this one, the things he says make it clear that he thinks the purpose of his existence is his work only. That he is worthless without it. I'm pretty sure that he hates himself, but we never see him talking or even thinking about it anywhere else. (There are lots of suggestions to it in his behavior and way of thinking, tough.) I think it's probably because he refuses to think about himself, his past, and his own feelings about his actions. For me, that's a clear sign of hating yourself.