Me neither. I've been known to hold a grudge for a very long time. I've gotten better at forgiving and moving on as I've aged but it - and patience - will never be my strong suit.
There is so much on the forum about cheating and how to recover from the loss of trust and painful feelings. It's a long, hard road if one really gets to the point of true forgiveness. Search for cheating, trust and keywords like that.
Is this the same partner that you've written about before here?
My only question is do you want to forgive him? What's in it for you? You stay in the relationship with him? If that's the price of admission for you to stay in the relationship, then is that worth it for you? Is he and the relationship you have worth doing the hard work of forgiveness? (I am speaking about both of you. It is possible to forgive those who never repent but I do not suggest staying in a romantic relationship in such a situation.)