There are times when a couple can both work fiercely on their own programs of recovery, and if they are both successful and diligent and committed, in time they can rebuild a strong relationship.
There are times when one person works hard on a program of recovery and for whatever reason the other person does not. The person not in recovery can act in a punishing, punitive manner and the person in recovery feels frustrated and unhappy in a dysfunctional, unhealthy relationship.
There are also times when there has been too much damage done to the relationship, that the relationship has become toxic. Each person can work on their recovery programs, but the relationship itself cannot be repaired.
It's hard to not be bitter - I know I was for awhile. But in the end, I was able to deal with it and understood that I was OK, he was (probably) OK but that WE would never be ok. I have struggled with the angry feeling that his next wife got to experience all of the good and healthy parts of him that I did not. I have struggled with the fact that he got his life and profession figured out, and that he makes well over 6 figures now, and when we were married we struggled, scrimped and saved. BUT in the end, each of us went on to live a happier, healthier life.
That's how it's been for me.