I can't remember where I read this, but it's a good lesson on making mistakes.
Landing a jet on an aircraft carrier is tough. It's a moving target; there are crosswinds — undershoot and crash into the carrier, overshoot and go off the edge.
Trainee pilots complete their initial landings with an instructor, who is ready to jump in and correct a mistake. There comes a crucial moment — the point when a trainee pilot can land by him or herself. To make this decision, the instructor does not look at the number of successful landings. Instead, the instructor waits until the trainee has made a mistake and recovered. This way, the instructor knows that the trainee can get themselves out of trouble if they ever get in trouble.
Being good at something is not about being error-free; it's about being able to make an error and still recover.