How did you finally forgive yourself when something made you feel guilty?

There are a lot of ways to cope with being imperfect. One of them is to realize that life is a class room, and that it is highly unlikely you will score 100% on every single test. Just as you learned to live with less than 100% on your tests in school, you can learn to live with making a mistake in life, and feel less guilty. Just promise yourself you will learn from that mistake, and that you will never do the same thing again.