I agree that losing through divorce is difficult rather than through a natural death like cancer or a heart attack. With a divorce that is not one's doing and one is fighting it all the way, then there is the guilt factor.
"What could I have done differently?" can be a constant source of unease. There can also be the hope that maybe I can win them back. Maybe there is something I can do. I have never found that to be true.
The best thing I did with relationships was not blame myself or that person. That is not easy but it is such a relief.
Hope you find some comfort and healing in this difficult situation.