Why would a man admit that one woman is the best thing that ever happened to him and then choose another woman that he knows is not good for him?

Some people dont think they deserve the very best for them. Whether its because of a martyr attitude or the self defeatist or how they were raised. They could have been told they dont deserve anything and believe it. Some people also choose the hard road because they dont know any other way. We are creatures of habit and seem to congregate towards whats familiar, whether it is bad or not. Maybe just maybe he is saying this for pity. Is this person one who cant get out of their own way and always seems to have problems, that for some strange reason is everyone else's fault. Some people cant live without chaos in their lives and like to drag others into it as well. Go figure?