Everyone screws up, and you will screw up plenty of times in your life. Forgive yourself when you make mistakes, because holding onto negative feelings about the past does nothing but prevent you from enjoying your life to the fullest.
Think of a specific thing you did that you feel badly about.
Call it up in your mind and focus on it.
Repeat the following to yourself while thinking of that thing:
“Holding onto my bad feelings about this is doing nothing but harming me and everyone else and preventing me from enjoying my life fully. I am an awesome person. I choose to enjoy my life. I choose to let this go.”
Repeat the above steps every day until you feel a sense of freedom or lightness around your issue.
It may take days, weeks, or months, but if you practice this action daily, you will be able to forgive yourself of anything.