When I say published I don't mean in a book necessarily, it could be a blog post or it could be read aloud or it could be share in a somewhat final format with another human being who helps you to make it better. But even with all of those things, sometimes we just need to reflect upon our own writing and our process in order to be better writers.
That is where reflection comes it. It isn't easy. I have found that I often had to explicity teach how to reflect - to both kids and adults alike. I really like this model from Peter Pappas:
How might you use this with your students?