It was long ago so I don't remember the details, it was part of Church process.
I recommended the following:
1. Understand that you are a sinner and that you wrong people very bad. In other words, recognize that you need forgiveness yourself.
2. Recognize that the other person is sinful as well.
3. Re-live the moment and recognize that it hurts.
4. Realize that the other person fucked up really bad. Don't apologize for them.
5. Forgive them. Thinking that if you don't, the problem will hunt you (not the other person).
Repeat this process several times during several years and you will be able to do it.
I recommended the following: 1. Understand that you are a sinner and that you wrong people very bad. In other words, recognize that you need forgiveness yourself. 2. Recognize that the other person is sinful as well. 3. Re-live the moment and recognize that it hurts. 4. Realize that the other person fucked up really bad. Don't apologize for them. 5. Forgive them. Thinking that if you don't, the problem will hunt you (not the other person).
Repeat this process several times during several years and you will be able to do it.