Guilt can be a good thing. It's a soul's call-to-action; the indication that something is wrong. The only way to rid your heart of it is to correct your mistakes and keep going until amends are made. I don't know what you didn't do and what you should've done, but the guilt? The guilt... means your work is not yet finished.
If I can have honesty, it's easier to overlook mistakes.
The road to genius is paved with fumble-footing and bumbling. Anyone who falls flat on his face is at least moving in the right direction: forward. And the fellow who makes the most mistakes may be the one who will save the neck of the whole world some day.
You do and it'll be the biggest mistake you ever made, you Texas brushpopper!