My xabf (my son's father) was/is a heroine addict. There are happy endings. I think it just depends on what your idea of a happy ending is. And realizing that with addiction, there never really is an "end." They're always going to be addicts. Today, my son's father and I are basically very, very good friends. But, that's literally years upon years later. And, the struggle that it took (the both of us) to get to this point almost broke me completely. Today, he's sober. But, he recently relapsed. And even though it had been years since his last relapse, I had to remember that nothing had changed. That I needed to keep myself and my role in the friendship in check and revisit all those lessons I had learned. Alot of it all, for me, was giving up on the dream that I had created in my own mind. Coming to realize that he wasn't going to some day just morph into the person I wanted him to be. He wasn't going to go back to how he was before he started using when we were together. That, as much as his addiction had changed me, it has also changed him. And, there was a healing process and a grieving process that I needed to go through before I could ever be at peace with myself, much less anyone else.
If I have any advice, I'd say, live in the present. Don't worry about the future. Take care of yourself. Work on your own recovery. And in time, there may be a happy place in your life, but you need to find your own happiness and not let it depend on someone else's actions.