I have learned to forgive myself through a practice in school. Particularly in math, the kids make errors and much of the time they are silly mistakes like adding 10 and 5 and getting 50. I tell them, these are minor and they will learn from them. We tend to cheer our mistakes since we truly do learn from them.
I learn from my cooking mistakes and while, I can't say, I will not leave an ingredient out, in the future, I am going to be more careful.
The resulting dish, although not a pie was tasty and we enjoyed it.