How do I better handle my breakup?

I got involved with my best friend who is married but has been very unhappy for the last five years. We both fell in love and have been together for eight months. He left the house and filed for divorce. He decided to tell her about our relationship, and she is willing to forgive and work on things. This shook him. They have two kids together. He decided to put the divorce on hold. He left town for a month to get clarity on the situation and see a therapist.