If you love him, this is easy

I believe this one-hundred percent and expect the same consideration in return(see below posting). The hard truth of the matter is that people do not change unless they want to change. It takes a lot of effort to change any behavior and if they truly don't wish to change it, it simply isn't going to happen.
So instead of trying to mold a person into what you think they should be either accept them as they are, or walk away. It is what is going to happen in the end anyways.