Whatever we expect with confidence becomes our own self-fulfilling prophecy. — Brian Tracy
This is no less true when we expect other people to succeed, expect them to do things correctly, expect them to give everything they do their best effort. You are surprised when other people make mistakes, give things less than their best effort, don’t succeed. Since you expect success, you assume personal responsibility for mistakes of others, lackluster effort, non-success. Your first take on the situation is that you haven’t been smart enough or skilled enough to effectuate the right outcome. You then work with the person to identify the deficiencies. You modify your performance so that you better facilitate the other person’s success.