Many of us struggle with forgiveness. What is it? Why do I still have feelings if I already forgave? What is the role of "forgetting" in forgiving?
I think our mistake is in how we view forgiveness. Anger - and especially resentment - are very active. When we harbor resentment, we have to actively carry it around with us. We think negative thoughts about the person (or ourselves), we ruminate on the event, we feel the anger in our body, we have fantasies of blasting the person with literal or metaphorical sticks and stones, we avoid the person. Active, very active.
Why would forgiveness be any different? Forgiveness is not passively releasing; It is actively letting go. With the same amount of energy that we held on, we actively release. We have to continually replace resentment with forgiveness - Think compassionately about that person, ruminate on loving kindness, feel compassion in our body, have fantasies of love and peace, accept the person. Active, very active.
Perhaps with time we will develop emotional muscle memory and won't have to be so actively mindful. But, until then, lets get busy forgiving.