Hmm, the forgiveness thing has been a huuuge issue for me. Being a Catholic helped a lot as it is ingrained in me whether I like it or not. Having said that, I was angry and felt hugely betrayed and I still feel hurt. So faith didn't get me across the line; what did help me forgive was the following.....
The best advice I got was from my father who said that I could choose to carry the anger and resentment around like a hot coal but that would not change anything at all or I could forgive my wife and see what came of it. Forgiving WAW said more about me than it did about her. My father was clever, he played to my pride in showing me that forgiveness made me stronger and better but it did not make WAW "right".
Pride is the big issue in all of this. I felt that WAW's EA/PA humilated me. I could not understand how 10 years could be replaced so quickly. Doing anything that appeared to say WAW's A was OK was totally foreign to me. Forgiveness was therefore also totally foreign.
But at the end of the day, none of that changed what happened. But getting over the humiliation and the fear of being humiliated again is a huuuge barrier to reconcilation of any kind.
But, all of that said, the EA wouldn't have happened of there hadn't been cracks in the M. So I took a long hard look at myself, with the help of both the DB and DR books, and saw that I had stopped communicating, was stressed, angry and generally unpleasant to be around. So, despite my being faithful to my vows and WAW not being faithful, I was a big part of the problem. I wish that realisation hadn't come from WAW's A because that has caused me a huge amount of pain.
What got me to forgive in the end was that I knew I could never make our M work if I did not. I still don't know if our M can work but I need to know for myself and for S3 that I tried everything I could.
Also, knowing that WAW is racked with guilt made me see that not forgiving her was also bad for our S3 who could sense the tension and intense emotions.
But to answer your question, the only thing you can say is that you are sorry, that you regret the pain this has caused and that you really want to see what you can do together, even propose some joint counselling.
-------- Me; 38 W; 34 1 4yr old S Married 4.5 yrs, together 9 yrs Bomb; 15 June 2007 Holiday together Sept 2008; My Dad dies Nov 2008; reconcliation fails Nov 2008