Think about what lessons you could derive from a session of forgiveness, as painful as it might have been. How can these lessons help you grow? Focus on the person who wronged you. What pain or anguish could they have gone through in their life that made them do what they did?
Remember that hurt people, hurt people. Those who hurt others are doing it because at some level, at some time, they were hurt, too. Think about how they may have been hurt in their childhood or in recent years.
The following forgiveness process could take a few minutes. Afterward, you should feel a slightly lesser negative charge toward the person who has wronged you. Repeat the process until you feel comfortable forgiving into love. For a serious offense, this could take hours or days. For a small offense like a minor issue with a coworker, five minutes may be all you need. I learned from this experience that you don't have to ask the other person to forgive you. You just have to forgive them. And that's completely within your control.
Now, there's something important to distinguish here. "Forgiveness into love" does not mean to simply let go. You still need to protect yourself and take action if need be. Criminal acts, especially, need to be reported to authorities. But the pain of what happened should not eat at you.
Here's how you can get started: