First, don't be afraid to fail and make stupid mistakes. Then, after you've made those mistakes, examine them and eliminate them. I think the author is talking about the latter part, and that often this process of removing mistakes is all it takes to be good at something. This idea could be reassuring to you if you tend to think that you need a certain genius that you do not have in order to excel. All you need is the ability to recognize your mistakes and the will to get past them.