You reach a crescendo of the feelings and nerve endings. It is the emotional and physical coming together. I still have problems forgiving my ex-husband. It is forgivable not in the sense that you should keep cheating on your husband or wife, but it is a wake up and a shake up and a cry for help. It is a dysfunctional attempt to stabilize a relationship.
Most relationships get better after an affair.
They realize what work they need to do to make a relationship work. It is a brush with death that gets people moving. The way you can forgive your ex is to take a look at the part you played, not that it is your fault. It takes two to tango. It is a symptom that we need to do more work in our relationship.