Om Swami
Why can't I forgive someone who hurt me?
Forgiveness grows from compassion
Forgiveness is triggered by a sense of compassion, as a mother forgives her child's mistake out of pure love. If you are trying to forgive and cannot, you are not being compassionate to the other person and to yourself.
If a child makes a mistake and the mother forgives him out of pure love, forgiveness comes from within automatically. What triggers that forgiveness is a sense of compassion.