Not negative, at all.
You can have compassion for the person with the disease without feeling responsible for it, or sacrificing yourself to it.
The thing to remember is that he HAS the ability to recover if he chooses to. If down-and-out gutter drunks can recover, he can. He may have to get worse before he gets better. That's how it is for a lot of alcoholics. But as long as you are there to "take care of him" why should he?
Hugs, you are processing things in a healthy way.