I believe all great writers develop over time, from reading other stories, viewing their writing styles, and developing their own. Personally, I've spoken to writers who specifically have improved through school teachings, but if a writer doesn't develop, even the slightest, then maybe they aren't meant to write. We all learn from our mistakes, but some of us are so far past ignorance or arrogance that they believe that they created grammar, punctuation, and their entire language. Some people never seem to learn. I thank the ones who do.