How do you stop the agonizing pain of betrayal after your husband's affair?

Good one and a hard one to answer. Some people never do and you will have to decide if you are one of those people. No one can make up your mind but you. What was damaged, among other things, is your trust and respect for that person. Those are HUGE items in a relationship. They are often reasons people are together in the first place...you feel that you can trust someone, you are safe with them, safe to confide in them, and that you respect who they are and what they stand for. Once that is damaged, it may never be the same again. However, that doesn't mean that it has to be over. It may just be different. LIfe won't go back to what it was before but if there are still things you love about that person, and you still want to share your life with them, you can make it work. Just know, if it happens again...it will keep on happening. Good luck to you.