My "cloistered brothers" and I were discussing the Gospel of Matthew 5: 43-46. Here Jesus is asking us to do something very hard--not impossible, but as close to impossible as one can get (sometimes).
(1) It's natural to hate those who harm you. Even a baby will slap at a mosquito. It's not because he wants to hate the mosquito, but rather he wants to stop the pain. It's as simple as that. Someone hurts you, you want to stop that hurt. The knee-jerk reaction to stopping hurt is to hurt back.
Once one recognizes this fact, then he can see that he may not even know the person who is hurting him, so how can he hate him? What he hates is what he is doing.
(2) Another thing to consider is Jesus' command "to love your enemies," itself. Think of the different kinds of love: agape, eros. Also, love is translated as "charity." So how do you love an enemy. First, think of love not as agape, certainly not eros, but as St. Thomas Aquinas in the Summa Theologica II-II, 26 teaches us, "To love in charity is benevolence: to will the good to a person or God...."
Hence, don't harm the person you hate. Think "Do unto others as you want them to do unto you." So push yourself to do something good to that person. Some acts of charity my "cloistered brothers" did for their enemies: nursed, made a meal and fed the person, gave them something they wanted, etc.
It seems that these acts of charity softened the enemies' stance. It was a visible difference.
(3) Be open and receptive to your enemies' gestures toward friendliness. Then talk. Talk again. Talk, some more. Communication should bring understanding. Understanding will dissolve the hate and soon you will find forgiveness.
That's the method we came up with.