Guilt is anger that you feel you have no right to have. Guilt is of no benefit to anyone.
Find the guilt.
1. Write down, in detail, the experience about which you feel the guilt. Don't try to write in any particular way. Write it as it is, as it was, and how you feel about it. Be honest.
As best you can, be the person you were at the time you felt the guilt.
2. Find the anger under the guilt.
3. "Who am I angry with?"
4. Feel the anger; really feel it.
5. Create all the anger that you did not feel at the time. Feel it. You may, at first, feel anger as grief or frustration or annoyance or any other feeling. If you do feel any other feeling feel it and keep feeling it, consciously, until you can feel the anger beneath it.
6. Feel the anger
7. Say all the things that go with those feelings especially those things that you did not say at the time. Say it aloud if you can.
8. Imagine any other person who was involved answering you just as you would wish them to do so.
9. Forgive everyone involved.
You may find so much anger that you will need to handle it as in "unwanted emotion".