Why did your therapist tell you to do this?

Anyway...

When I was manic, I did some really stupid things, including cheat on my husband with over a dozen men, most of them I didn't even know their names. Just one-night-stands. I still live with the guilt, several years later. He has forgiven me, because he knows I was not myself at the time. But I don't know if I will ever forgive myself.

You need to somehow get to that point where you can forgive yourself. Realize that you were not yourself when you did the things that you did.