I think I could forgive if the person truly showed remorse. When they can't and you know they could care less about what they did, one still needs to let go, but how?!
I think you're mistaking forgiveness with letting go, and that's the problem. It's very possible to stop dwelling on the incident/person without actually forgiving them...you just cut them out of your life entirely and the whole 'out of sight, out of mind' phenomenon takes over. At least, that's what happens when I do it after awhile. At first, it consumes you several times a day...you can't help but think about the whole mess and get angry...but eventually you think about it:
-once a day, then
-once every few days, then
-once a week, then
-once a month....then less
I've had two betrayals that I have not forgiven.
One was a former friend who talked shit about me behind my back so he could look cool in front of some of his co-workers. I have no need for people lacking loyalty in my life, so I cut him out completely. I was best man at his wedding...had been friends for 10 years...but that didn't matter to me. He tried to apologize a couple of years later through a third party, but by then I was perfectly happy with him not being in my life, so I chose to keep it that way.
One is a little more complicated...my 13yrs younger brother and I haven't really spoken much in the past 2.5 years. Loyalty issue again, plus some shit drama he brought into my parents' lives also. All I ever wanted was for him to get rid of the crazy bitch who started all the chaos, and the heartfelt apology he owes me. The bitch is gone, but the apology never came. He can't man up and admit he was wrong and apologize, so we will remain estranged until he grows a pair and does the right thing.