You really cannot "learn" to forgive him. Your subconscious will not allow it as it sees forgiveness as a way of losing safety. This is not a job for a psychotherapist, it would take them years and a ton of money to get you to feel a little better.
But forgiveness or letting go of the energy is very possible and much faster than you can imagine.
Frankly I don't see any other way. So many come to me with ailments because of lack of forgiveness. They swear they forgave, but all they did was remove the problem from consciousness and bury alive in the subconscious.
Let me put it this way: With psychotherapy it takes an average of 5 years of weekly therapy to rid oneself of the trauma of rape.
With a skilled energy therapist it will require one to three sessions.