It must depend on what you are being asked to forgive. Some things, nobody can forgive except perhaps a genuine saint, and perhaps the world does not expect them to forgive. I am thinking of tragedies like harm to a child caused deliberately by someone with bad intentions. If I were that child's mother, I would almost undoubtedly not forgive, I don't think. I also think that for some things, the price of not forgiving is very high. In the example I gave, if it became clear to me that my continuing to be furious would only harm me, and not the person who originally had the bad intentions, I might try to at least let it go so I myself would not be harmed by my anger. For that, I would seek therapy from a good counselor. Have you tried that?
True forgiveness comes from letting go of all the pain and the hurt. I know it is easier said than done but believe me, when you learn to truly forgive, you will be the one benefiting most as you would feel free and light. When you forgive someone who has deeply hurt you, you are doing yourself more favor than the other person.