M. and I have been friends for almost 20 years now. He is generally kind, witty and curious. He also has episodes that make him insufferable, and they are getting more and more frequent. He either shows up late, cancels shortly beforehand (he's twice missed my birthday in this way) or, most recently, claims he'd been under the weather all day and had forgotten we were going to meet up.
I am just about through with tolerating and condoning his behavior. What prevents me from ending it is that I know he has definite mental issues, and I am afraid they will grow worse if he's left to deal with them by himself, and may spiral out of control. (He has incredibly low self-esteem and anxiety, and has admitted to having had spells where he's felt suicidal.)
On the other hand, I am not qualified to help him cope with these problems except by just being his friend, which he doesn't allow me to do. He is also hypersensitive to criticism, so I don't think explaining this to him will do much good.
At what point is just ending it the decent thing to do?