I'm dealing with a similar issue of needing to forgive someone and I don't believe forgiveness comes easy all of the time. It's not impossible but I don't think it's something that happens overnight for most of us, and sometimes, it might even take years to FULLY forgive. I do know one thing, by being open-minded and recognizing it's something you need to do, that's better than where you were yesterday and if you're honest with God and tell him "God, I'm inspiring to be more Christ-like but God, I need your help, I'm having trouble forgiving, please give me strength when I'm tempted to cling to the negativity when I know you want to free me from those feelings." Gradually, you'll find yourself letting go and each time you have to deal with those feelings, you'll gradually release them too by being honest, speaking on the faith that you have in God restoring you. And don't forget, even if in a year you're still dealing with some feelings of negativity towards that person you're closer to where you need to be than where you were. We're works in progress!