If you have not found a way to forgive which works for you, you might try this. Every day, ask God to bless the person you are resenting. Keep doing it until you experience a shift. You will discover that you've totally have forgotten why you are asking for this blessing. :-)
In the long run, it's not a question of whether they deserve to be forgiven. You're not forgiving them for their sake. You're doing it for yourself. For your own health and well-being, forgiveness is simply the most energy-efficient option. It frees you from the incredibly toxic, debilitating drain of holding a grudge. Don't let these people live rent free in your head. If they hurt you before, why let them keep doing it year after year in your mind? It's not worth it but it takes heart effort to stop it. You can muster that heart power to forgive them as a way of looking out for yourself. It's one thing you can be totally selfish about. Doc Childre and Howard Martin
The remarkable thing is that we really love our neighbor as ourselves: we do unto others as we do unto ourselves. We hate others when we hate ourselves. We are tolerant toward others when we tolerate ourselves. We forgive others when we forgive ourselves. We are prone to sacrifice others when we are ready to sacrifice ourselves. Eric Hoffer
I worry about fast forgivers. They tend to forgive quickly in order to avoid their pain. Or they forgive fast in order to get an advantage over the people they forgive. And their instant forgiving only makes things worse...People who have been wronged badly and wounded deeply should give themselves time and space before they forgive...There is a right moment to forgive. We cannot predict it in advance; we can only get ourselves ready for it when it arrives...Don't do it quickly, but don't wait too long...If we wait too long to forgive, our rage settles in and claims squatter's rights to our souls. Lewis B. Smedes - The Art of Forgiving