For every mistake you make, surely you blame yourself, even just a little bit, for doing something you shouldn’t have. Now, even though it’s just a little bit of blame, that still has a lot of effect on your confidence. To avoid this from affecting you gravely, forgive yourself. Tell yourself that’s absolutely alright to have made a mistake. Everything will turn out alright in the end. You can fix it. Also, just treat this situation as a learning experience. After all, the only way you can totally avoid mistakes in goal setting is to experience it firsthand.