From Meditation for Beginners by Jack Kornfield, K1250D:
When you offer forgiveness, you can also say that what happened was wrong and that you will never allow it to happen again that you would even put your own body in the way of letting such harm come to another person in the future. But forgiveness is the act of not putting anyone out of your heart, even those who are acting out of deep ignorance or out of confusion and pain. Forgiveness is also a matter of letting go of the past and knowing that even though something was wrong, the way to go forward is to start over.
It is also important to understand that the practice of forgiveness is a practice, which means you might do it 50 or 100 or more times before achieving an authentic sense of forgiveness in your heart. Some part of the process may involve rage and outrage, and some of it will probably involve grief and sorrow. Sometimes what arises in this process is that for the first time we fully come to understand how much anger we still carry and how deep our pain is.
In a way, sometimes forgiveness means simply that we choose not to carry the hate inside us any longer because we realize that it is poisoning us. There is a story told of an American ex-prisoner of war who met another ex-prisoner of war many years after the Vietnam War. One prisoner of war asked the other, "Have you forgiven your captors yet?" The second said, "No, never." The first POW looked at him and said, "Well, they still have you in prison then, don't they?" It's important to realize that the extension of forgiveness most powerfully affects the person who is offering it.
At first, people may find that offering forgiveness feels artificial or unnatural. It is fine if that is the way it is for you; you can just do the meditation and be receptive to whatever happens. Sometimes you will even experience the opposite of compassion, such as anger or frustration or emptiness. If this is your experience, you should hold those feelings in lovingkindness.
There is a place in everyone that yearns to love, that longs to be safe, that wants to treat others and ourselves with respect. Sometimes that place is buried underneath layers of fear, old wounds, cynicism, and pain that we have used to protect ourselves from injury.
So once again make yourself comfortable, let your eyes close gently, and come back to the breath. Let your attention be soft enough that you can feel the slightest movement your breath makes.
First you ask forgiveness for yourself for when you have hurt or harmed anyone in thought, word, or deed, knowingly or unknowingly and we all have. We all at times act unskillfully out of our own pain and fear. Allow these instances where you have harmed others to come into your mind and heart and ask forgiveness.
Then ask forgiveness for the ways you have hurt and harmed yourself out of fear, pain, ignorance, neglect, and dishonesty. Let the images of all of the ways you have hurt or harmed yourself come into your awareness and ask for forgiveness.
Finally, let the wounds and sorrows you have suffered at the hands of others come into your awareness. Realize that you have been wounded and hurt by others out of their fear, pain, and confusion. Feel the places in your heart where you hold resentment and touch them with kindness and forgiveness, and see if it is time to let go. Then, to the extent that you can at this time, extend forgiveness to those who have hurt or harmed you knowingly or unknowingly in thought, word, or deed.