When I have been in these relationships where the other person had a drug or alcohol problem, I also thought I would 'help' them. I've learned that when I see that someone ELSE's life is messed up or needs to be lived differently, but that person sees nothing wrong with the way they are living their life, I am the one who gets out of control. Whenever I have analyzed and overanalyzed the situation (which has been plenty, trust me) I may have thought I was the right one (because of my so-called good intentions) but in reality all that was was obsession.
Can't help nobody who can't see there is anything wrong.