You're right, forgiving is difficult. It's easy to say that you've forgiven someone, but it's hard to let go of the anger or resentment when you recall what they did to you. I don't know if it's because I've matured, but lately, when someone wrongs me, I find myself giving them reasons or excuses for why they did things that offended me, just so I can forgive them. I always tell myself, "Whoever has understanding, let them be the one to comprehend."
In the end, the hate or anger we hold against those who offend us affects us more than it does them.