The modern day theory of mastery prescribes 10,000 hours of practice. That’s not a magic number, of course, it’s merely a guideline. But more important than the number of hours of practice is the quality of that practice. Practice needs to be focussed and deliberate. And you must also fail. In fact, better than 10,000 hours of practice are 10,000 failures. Even better is to use your failures.