I will pray that one day you will be able to forgive. I believe it is also a matter of perspective. I was most unforgiving toward my Ex, not for the ending of our marriage so much as how he treated me during the divorce process. He has yet to apologize or at least admit that he treated me awfully as well as going against his promises he made at our wedding. However, I do believe that the Holy Spirit helped me to change my perspective to try to see it as God may see it. From His vantage point, even though I have been hurt terribly, I myself am also guilty of hurting others- to a lesser degree or greater- I realized that it did not matter, but that since I was not free from sin myself, how could I cast a stone by refusing forgiveness and mercy toward another if I expected God to forgive me and be merciful.
Also, it is important to remember that forgiveness is not saying that you are okay with what they did or that it was not an evil act that was done.