I'm so sorry you are in this mess...it seems so monumentally unfair to suffer so much because our S is stuck in selfish mode. Believe me, I've been on the same roller coaster. Still am, but I'm learning to manage the highs and lows in a way that makes me feel in control and happy.
Most of what I've learned is on this thread...as well as reading others. And it's taken some plain ole' time too. Everyone says, GAL, find ways to make yourself happy, etc. At first it seems like it's just all repetition, but when you truly take it into your heart and make an out-loud-to-yourself decision to do these things, it's amazing the freedom you can find in yourself.
When I start to think about H and his As, the countless nights I was home alone, exhausted after days with tiny children while he was out living his secret single life...or the fact that though things are better between us now, he is choosing to live with his parents, I stop my mind from going there. Sometimes I have to do it out loud, most of the time, I just focus in on affirming thoughts that make be feel better, that point me in the direction I truly want my life to go. Sing a song if you have to. Anything that gets your mind on a different track. But learn how to do this, and you can do anything.
The Law of Attraction states that anything we focus our attention (conscious or not) upon will manifest itself in our lives. It cares not if we truly want that thing or not.
Anyway, that is what is working for me. GAL is more than just getting out and trying to busy yourself--leaving your troubles behind. It's accepting reality for what it is, and choosing to find the happiness and peace within yourself regardless.
So that's it. It takes practice, and I'm sure I'll still have struggles with it. But it does work.
((Hugs)) and best of luck. Learn to love you, and what your H does will no longer matter--because you will be happy in the long run despite any outside circumstances.
