One central lesson I have learned recovering from psychosomatic pain disorder, which is very much rooted in past trauma, is the imperative to forgive those who caused or contributed to that trauma. In fact, as a general rule I think most experience a pattern of trauma throughout their life on some level, if not in a severe way, such that the longer it is unresolved, especially through forgiveness, the longer it affects your physical health and consequently your whole state in life. I imagine this accelerates aging for many people.
The mind is so powerful that a mindset of peace and confidence (in God), and positive thinking, carries the person far, whereas a mindset of inner turmoil and doubt, engulfed in negativity, leads a person downhill. Lack of full forgiveness causes unresolved memories which can cause illness and bad habits, whereas good, healthy thoughts to heal those memories conversely restore health and better habits. Life only gets better.
There are two levels of forgiveness, moral and psychological. Moral forgiveness must happen as soon as possible after harm is done, and can be done quickly. It is a singular choice. But psychological forgiveness is a longer process of inner healing, yet still moral in so far as you commit yourself to that process. Forgiveness doesn’t necessarily mean reconciliation, but letting go of undo anger and resentment that automatically swells up in us after being injured, because of original sin. Note this does not mean having zero anger ever again to that person, as anger is the emotion the causes us to avoid evil and defend ourselves and others. So as long as said person persists in their ways and should ever cross your path again, having a modest degree of anger for that purpose is not evil, though perhaps usually it is wiser to be so mentally detached from them to be stoic.
There are ways to work on psychological forgiveness. One, every time past memories of your past enemy resurface, pray for them. Two, write letters of forgiveness to past enemies, being brutally honest what they did but also your own mistakes, but never send it or show to others. Instead do a ceremony of burning the letter as a symbol of letting go, praying to God saying “I forgive them.” Three, include in your prayers each night “and for past and present enemies.” For a moment think on those who most come to mind who need your prayers that they have conversion on some level.
Not yet achieving forgiveness is typically because of chronic obsession, not just about past difficult people but about life, which can be one form of demonic influence. The devil uses your past trauma to torment and sew seeds of doubt and despair, at least emotionally if not willfully.
So if you struggle with obsessing about past enemies and what they did to you, or any obsession, you have to do spiritual warfare against this every day, invoking St. Michael, praying daily for deliverance and to achieve a state of peace, and rising above it all through daily mental prayer, like an eagle soaring upward in the sky.
Forgiveness means “letting go” of everything related to the trauma of what that person did, becoming totally detached from them and the nitty gritty details of those memories (though not forgetting the basic fact of what they did to prevent it from happening again), healing, and therefore being transformed, all of which will happen when done through Christ, the sacraments, a daily schedule of prayer, and the clear intention daily to forgive your enemies.
In the end God will deal with them in a perfect way of divine justice, and your new tranquil state of “having forgiven” will show you the way to freedom from the evil they cause. In the end you will win and prosper from it. You do this by rising above and beyond your enemies through the power of forgiveness, imitating Christ.