Dangling at the end of an unattached heart string

So there's this guy. Isn't that how all great stories begin? I've known this guy for about 2 1/2 years, off and on, he's touched down in my life. Sometimes when we're off again it's on good terms and sometimes not. Truth is, he should've been long gone by now. He was supposed to be a fling. You know, one of those "no strings attached" deals where you don't owe each other any explanations, there is no exclusivity, and you aren't supposed to get your feelings involved. 2 1/2 years ago, I actually thought that kind of relationship was possible.  I am here to tell you now, 2 1/2 years later, it is not. Inevitably, one or both of you ends up with feelings. Good ones, bad ones, a combination of both, that's just human nature. Why else do you think I would keep letting him come back into my life despite his treacherously suicidal tendencies towards behaving badly? 

See, this guy is a raging alcoholic, and I mean of the worst kind. It's amazing he's still alive. If he even is still alive. The last time I saw him was Christmas Day. I told him that every time I see him, I wonder if it will be the last time I see him. Because, eventually, one of these days, he is going to disappear from my life forever, and I'll never see him again or hear from him again, and I won't even know what happened. One day, he'll just be gone. Do you know want to know what he did? He left without saying goodbye. I really wasn't expecting "one of these days" to be that one. Is it easier on me to have him leave now, before he kills himself? Before I have a chance to have any more feelings on the matter? At this point, is there any other way for this thing to end? Maybe it's already over, how will I know?  I'm just a girl out here dangling at the end of a heart string that is apparently not attached to anything. 

Am I supposed to reach out and try to help him? Am I supposed to cut my losses and delete his number from my phone forever? These are the same 2 questions he leaves me with every time he disappears. No strings attached, huh? It's really hard to answer emotional questions when your feelings aren't supposed to be involved.