That's exactly what I had to do with a friend. He wasn't a user per se, he had other problems he couldn't get a handle on that caused him to leap from one financial crises to another. I just said no, I cannot lend anyone any money any more ever because I just couldn't afford it. I also told him the favor bank had a zero balance and he needed to make some deposits if he wanted to remain friends. He was fine with it and we remained friends for years but I always had to set strong boundaries with him. You also have to have boundaries with yourself so you don't end up letting it make you feel guilty.