Release the past
I found this ... "To be able to become friends with ex-bf, it takes big heart to forgive and forget all the mistakes he's ever done. With this, your relationship and the ex-bf can be maintained. Also, do not let the desire to reconcile the basis you want to be friends with him. This will not work because it is the wrong kind of motivation, and if the motivation is wrong, then the action taken is also likely to be wrong."
and this too ... "Whether alone or as with the former, do not ever remembering the beautiful things that ever happened in the past. This would make him uncomfortable, especially when he's got another lover now."