I'm beginning to come to this realization myself - having balls is one of the most important factors of having success (no matter what success means to you, whether it's social, financial or something else).

If you don't have the balls to do the things necessary to archive the things you want, with all your energy and will behind it, you simply won't archive it.

Most people doesn't even try to do the things they fear, just a small minority does. Of the small minority just a few tries with everything they have, most of them unfortunately holds back because of their fear of failure. A fear of failure is preventing them from giving it everything they've got.