Do you feel sorry for him? Because I find that I usually feel sorry for them and when I do, it makes it worse for me. I've realized that feeling sorry for them does not help them, and actually hurts them.
Another thing is the memories of the good times. For me, it is better to keep telling myself to stay in the Present Moment. It is better for me to get as busy as I can with my life and stop thinking about the past. What's done is done and there is nothing I can do to go back in time and fix anything. I never had that power to begin with. Accept that Dr. Jeckyll and Mr. Hyde are one and the same person. You cannot have one without the other. Yes, it is sad, and yes, it is horrible, but you are doing the right thing. It will get better, I promise you.
I am sorry you are hurting. I have been hurting too. Please surround yourself with positive, supportive people. (((hugs)))