I can see why you'd feel bad, but don't beat yourself up. It happened....and you can't undo it. Let me ask you something: While the hooking up was going on, were you detached? I'll bet you were (otherwise, I doubt you could complete the act). Grasp onto that. Someone else found you desirable. Rather than let it destroy your self-esteem, remember that her leaving isn't all about you. Remember the detachment and hold onto it. Use it to your advantage when you interact with her. Think when you are around her, "there are other fish in the sea. I'd prefer you, but I know other women find me desirable". I don't recommend you go for a repeat performance unless you are ready to ditch your marriage, because honestly, you've now cheated also.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer
