Hmmmmm. If he's telling you he feels 'great' after just 2 months sober, I suspect that he could be whitewashing things a bit. Is he actually working some kind of recovery program? If he is using AA or other 12-step program perhaps you will hopefully see some kind of amends eventually, once he's become ready to take inventory (for me, I was nowhere close to brave enough for that at a couple of months sober).
As far as letting stuff go, (resentments and harms that other people have done to us) so that you can feel better, I think the trick is to stop thinking (initially at least) of this as forgiving and forgetting. Letting it go is different to that. I needed to make a decision that I wanted to feel better, and really recognise that holding onto it only served to punish me myself. Holding onto resentments is like drinking poison and expecting the other person to die. When we churn ourselves up with anger, the person we're angry with often remains unaffected by what's going on in us. Going over resentments is just putting ourselves through the same pain again and again that we sufferers when it was done once. The perpetrator is guilty of the one time they did the said harm. But we can then self-harm with the same event over and over and over. Like them stabbing us once, and us spending years stabbing ourselves in the same spot to remind ourselves what it felt like.
It is hard to break the cycle though. For me, childhood memories especially were played and replayed. That record never seemed to wear out. Until I decided I deserved better, and resolved to stop playing it. Not because I had forgiven or forgotten but because I wanted to be happy. I wanted to be free of all that anger and fear. And if those thoughts pop in my head again I ask myself "Berry. Do you want to be happy or do you want to be right?" And given the choice I'll take 'happy'.
I found that reading and finding out about codependency really helped me to find the willingness to let the stuff go. Especially some recovery of the inner child work that I did (I think that was from a Penny Parks book), but that might not be so helpful to you if you came from a less disfunctional background and experiences.
Sorry if this sounds a bit waffley. I've got a bit of a head cold and my thinking isn't up to normal muster at the moment.
Wishing you all the best for your recovery. BB