Letting Go of Anger
To maintain anger at someone over any period of time your mind has to work pretty hard. First, you gather together selected negative qualities and create a caricature of the person in your head. Next you have to continuously review the negative events that confirm the validity of your caricature. Then you rehearse arguments in which you prove how right you are and wrong the other person is.
I most often see this happening with family members. Through the hurt and pain in relationships with parents, siblings, grandparents, etc., a rigid caricature gets created over time. When you see these folks infrequently as an adult and don't heal the pain in these relationships, you can continue to feed the anger at them.
Letting go of anger usually starts with being able to offer yourself empathy or receive empathy from another about the pain you experienced and the needs unmet. With focus and inner work, you heal, reclaim your needs and learn to meet them consistently. You then may find that you have space feel compassion. You might start letting go of anger by taking a broader view of the person. You can start simply with basic facts of their life. Where did they grow up? How were they treated as a child by family and peers? What did they do well as a child? What challenges did they face? You can continue asking these kinds of questions as you look at each stage of their life.
After an intense period of doing my own healing work, I began unraveling the caricature of my father. First, I moved from seeing him as an abuser to seeing him as someone with mental illness. Then I began to see his suffering. Then I began to see him as a hurt child. Slowly over time I began to see and appreciate his heart and his gifts.
Anger is often an important part of a healing process. Anger is a signal that you are recognizing unmet needs and that you want to fight for them. Anger can provide the initial momentum for you to set boundaries and ask for what you need. It's easy to get confused and unconsciously believe that it's the anger that allows you to get your needs met and keeps you from getting hurt again. In actuality, it's your ability to name your needs and honor yourself that keeps you healthy and safe. Knowing this you can begin to let go of the anger and feel compassion for those who have behaved in ways that didn't meet your needs.