Visualize the face of the person who's hurt you. What do you see?
You may first see their expression in the moment of the event that they hurt you. It may be a face of anger or frustration, but keep looking at them longer and their facial expression will begin to change.
See their face in other moments. Visualize their face in moments where they have felt suffering. See them crying, perhaps, in one moment, with you holding her in your arms. See them laughing, in moments where they felt free and spontaneous. See the moments when she was doing something very ordinary, and you saw how beautiful she is. See her face when she is angry, and see how her vulnerability and suffering is masked behind her angry words and expression. See her in pain, when she sprained her foot while hiking. See her in the throes of passion and pleasure, the expression on her face at the height of orgasm. See her face anxious, worried about finding a job or getting the right grade in a class. See her face in love, looking into your eyes, looking out at the world. See her face in moments of true happiness, when she's not even aware of it.
Visualize this person, and see the forms of emotion morph from one to the next over the transparent image of his or her face. Watch the individual images blur, quicker in space and time, gradually, until you can see all of these faces of the person at once. Until finally, all you see is the person itself.
You see her just as she is: a painful yet beautiful expression of every emotion that belongs to the human experience. Transient, striving and searching, trying to live the best she can, find happiness, find love, traveling along a long path of burning desires. She is of the same nature as your self. We are intimately related.
Then, apply this process to others in your life. Take a moment to see each person important to you in this stream of events. Widen your circle farther until you see everyone in the world like this all manifestations of the human condition, including yourself.
When I realized this, everyone became my brothers and sisters. Everyone became family.