Forgiving your partner's affair is one of the most difficult things to do. One of the most important things to realize is that even though you may decide to forgive your partner, it doesn't mean that you will be able to. All you can do is to try your best. I advise those who want to forgive their partner to write a forgiveness letter in which you express all of your feelings of hurt and disappointment and desire for this to never happen again.
Of course, forgiving is very different from forgetting. We cannot intentionally forget. In fact, research on intentional forgetting shows that the more people try to forget something or not to think about something, the more they end up thinking about it. That's what's called the thought suppression paradox. So a lot of time, it takes a lot of effort and a lot of time to be able to forgive someone.
Another element of forgiveness is that the person who committed the transgression has to offer what we call a power apology. "I am sorry I did this," it simply won't do. It has to be a real apology coming from the heart, and that sort of apology has to include three R's. One, repentance, meaning, regret and remorse. I really do regret doing this. I feel awful that I cheated on you. Those are very important. The second one is rehabilitation, meaning, I have changed. I realized what I did was wrong and I would never do it again. And the third one is restitution and that is, what can I do to make you feel better? I would do anything to make you feel better and that may include, again, relocation or changing a job or whatever it is that the wronged spouse may ask of the person who had cheated on him or her.
So the power apology is very important to facilitate forgiveness, however, it does not guarantee forgiveness. It is a road that is a difficult and thorny road for the aggrieved spouse or partner and that may take a lot of time and effort.