When you are trying to forgive a person now for a recent injustice and you find yourself having trouble forgiving, please try this: Think about someone in your past who hurt you in a similar way. Have you forgiven this person from your past? If not, then he or she may be the stumbling block for your forgiving a person now.
Take some time to go back in time and repair your heart from the previous person and incident. Once your anger is diminished from that, then try forgiving the present person for the present injustice.
You see, you may have double-anger now, at the present person and the past person. Eliminating your anger from the past may free you a little more to forgive those in the present.