Take driving, for example. At first, you'll be nervous, but with deliberate practice guided by a tutor, you'll get better. When you reach a base level of competence and pass a test, you'll get your license and be on the road. 

But for years, you'd find you haven't really gotten better at driving. You only reached a base level of competence that will get you by and that's it. 

The same goes for writing. School teaches us how to write until we reach a certain level of competence. But we don't get better by practicing what we already know. And that's because we are hard-wired to avoid pain.

Getting better at something means we have to know what to improve on and work on that. But It's in our nature to avoid pain. And getting better at something sure sounds like it would require a lot from us.

So we resort to practicing what we already know, shying away from what we don't know ...