Thank you for the reminder. We are all only human, and need to keep in mind that fact. You are not God and you are in no position to ultimately judge. You can only control your own reactions.
It does no good to keep wounding yourself by revisiting an old hurt when that person likely doesn't even remember giving it to you. You don't have to let it happen again, but allowing the scar to heal slows and eventually stops the pain from oozing out.
RE: Forgiveness. Give it a try.