Try very hard not to waste too much energy regretting the rather long time you were together. I am NOT going to suggest you focus on whatever was good during that time, because at this point you probably can't recall much that was good.
After twenty-five years of marriage my husband met another woman and decided he'd rather be with her than with me. I also felt very betrayed, but at least our two sons were essentially grown, and I did not have to be a single mom like so many others. He and his new wife actually have a good relationship with our oldest, for which I'm grateful. That actually allowed me to move 800 miles away and start my new life. It's my personal opinion that if it's at all possible to relocate, it should be done.
Younger son has essentially no relationship with his father, which is too bad, but I'm not going to push that. This son moved himself even farther away from home, and I honestly think that my move allowed him the freedom to go. Had I stayed in Kansas, son 2 would have thought I needed him to stick around. All three of us are doing quite well, and I simply don't care how my ex is doing.
It's been six years since the marriage ended, four since the actual divorce. I got through the first couple of years with the help of a lot of wine. It worked for me. I now tell people that in my most optimistic fantasies that my marriage had not ended, I don't think I would ever have persuaded him to leave Kansas. I moved to Santa Fe and I just love it here. It's been good to me.