You may have made mistakes- we all do- you did the best you could. Looking back it is easier to see what we could have done differently. Yet doing it all "perfectly" still might not have saved your M. I try to do what I can live with morally and don't do great DBing- wish I could do better. My D has started yet I will be able to live with myself knowing I did the best I could.
I often feel my H is my soul mate and worry that I won't ever be truly happy in a R again- but I don't know what is around the next corner and I'm trying to enjoy that mystery.
Finding happiness within ourselves first - the rest will come!