I agree that anger can serve the one who was betrayed. A betrayal shifts power to the betrayed, and the anger serves an advantage in that way. I think that the “how to forgive” is difficult but possible by developing some empathy for the one who betrayed you. What was going on their life to lead to this deception?
With my wife, I learned to understand what life had been like for her as she also began to find out what I had experienced. I do think that forgiveness of each other resulted from that compassion for each other’s life experience, and not just through finding new partners.
But until the anger is fully vented, it is difficult to find a reason to empathize with the deceiver.
Thanks for your comment.