That's tough, Sizzle Squid, but yes, I think you have to move on - mainly because you can't go back when things have changed.
But it sounds as if there are upsides: you've had the chance of therapy which has given you a better insight into your motives and hopefully made you happier.
It's not necessarily a good idea to simply cut yourself off from your past, though (is it possible that all this was caused by your trying to suppress an earlier bad part of your life?) Rather than trying to blank it out, better to allow yourself to remember it but also remember the many other good things that have happened to you, and to keep them in proportion, rather than just obsessing about one episode. You sound like a good, sensible person. Some day you may be able to be friends with him again, but not till you're sure you're over him. Good luck.