Practice and delivery.
Amateurs practice out of passion. They practice until they get it right.
Professionals practice out of obligation. They practice until they can no longer get it wrong. Never lose your passion like a true professional, but practice until you can’t get it wrong.
The amateur fades at the line, the professional delivers every time.
If you don’t deliver, you’re still an amateur. Don’t worry, knowing you’re an amateur is a huge step toward becoming a professional.
If you’re an amateur, keep practicing because you will get it right. The key is to keep going after you’ve gotten it right.