You've just got to have a sense of respect for the person you have children with. Anger doesn't help anybody. Ultimately you have to say forgiveness is important and honoring what you had together is important. But it's easy to say and harder to do.
So many people prefer to live in drama because it's comfortable. It's like someone staying in a bad marriage or relationship - it's actually easier to stay because they know what to expect every day versus leaving and not knowing what to expect.