I had lunch today with my good friend Scot. An old friend had sent him a collection of short stories that she'd written some years ago and published herself. When I asked him if they were good, he said "Not very. There were some great ideas and some beautiful images but it wasn't well written. It was as if she put them down and then gave up."
Having a willingness to work at our writing is an essential characteristic of the good writer. That may seem obvious but I don't think so. Many writers think that when they've labored through the self-help book or the novel they've always wanted to write, read it over, and tweaked it, that they're done. It doesn't occur to them to rewrite it because they never have been shown how.
When I talk to clients whose work seems hasty and amateurish (although it may have taken them several years to get it that far), inevitably they did a first draft for school work, maybe even college work, and got good grades. That makes them a good writer, they think. They don't realize that teachers aren't always good judges of writing, that teachers can be poor writers themselves or only look at a student's grasp of content for the grade.
In order to become a good writer, one must read a lot, write a lot, and usually do some study of the genre and style. That can be formal study in classes or it can be self-study, a close reading of text to see how the greats do it. In any case, working and reworking with the writing is the only way to get it to be really good.