I started writing when I was ten.
Whenever it was I experienced this, I don't remember. My stories went from Mary-Sue to realistic over the course of a few years, mostly by exposing myself to authors who were just better than what I'd read before. I built on top of that until my writing was what it is now. I'm happy to say that's still evolving, as it's under my impression that no author should simply stop progressing in writing style.
Whenever it was I experienced this, I don't remember. My stories went from Mary-Sue to realistic over the course of a few years, mostly by exposing myself to authors who were just better than what I'd read before. I built on top of that until my writing was what it is now. I'm happy to say that's still evolving, as it's under my impression that no author should simply stop progressing in writing style.