First, think about if want to do good work (that you can say this is good). How to know if you are not convinced of that? If it feels like you need courage to

First, think about if want to do good work (that you can say this is good). How to know if you are not convinced of that? If it feels like you need courage to fix or redo something. Similarly, if you boast about your courage. To me that's the difference between an A and B player, both are good but for B doing good work is somehow painful. To answer your question, since nobody is omniscient, realize that if you feel bad for making an honest mistake you are fighting Nature.