I completely hear what you are saying, but from my perspective I did something similar and i feel that it back fired on me as far as reconciliation goes. So if you do have any hope of reconciliation don't do a letter at this point. My husband is still in contact with Ow. When I first found out about the affair and i thought we were in reconciliation I took so much of the blame on myself. I opened up to him about how selfish I had been and how I hoped that he could forgive me for my mistakes in the marriage. We started to read the Dr. Phil book together, and I was very open about the issues that I felt I had brought to the marriage while we read that book together. Well, as my husband got back in touch with the OW he would bring up the fact that this made him aware how many problems we did have in our relationship and how I was really to blame for a lot of them. My point is when they are in the fog, they are already rewriting history and blameshifting. You don't need to do anything that helps them to do this even more. If you get to a real reconciliation then it makes sense to do this. Or if forgiveness is what you really want and you never make it to R, then wait until the divorce is over and see if you still really need it. In the meantime, don't feel to guilty about what you did wrong in the marriage. The bottom line is he never gave you a chance to fix it.