It probably sounds simple but
what I did when I left my AH, I found myself missing him and romanticizing the good times. To counter that, I created index cards of specific incidents that either solidified my position to leave, or embarassed or harmed me. When I got to missing him too much and only remembering the good times, I read a few of those cards to remind me of the "full picture" and try to keep my decision grounded.
I was not married for a very long time, but I was completely in love with the man, and it took a long time to get over it. This was 18 yrs ago and I have not remarried. But I am able to let that relationship go now. I hope you find equal peace soon.