Too many writers never finish their work. They move on to other things long before getting to the finish line. As a result, they never develop the part of the craft attached to the process of finishing.
I understand perfectly well what is happening inside the writer. I have it myself. All writers have it. It's part of our way of thinking.
We become so good at inventing characters and plots that we can do it on the fly. Any situation we find ourselves in leads to shaping the initial patterns of a story in our mind. It becomes second nature to us.
The real work
Overall that's a good thing. It's a sign of perceiving the world as a writer, which means we are on the right track.
Having said that there is a bit more to writing, and most of that bit is where our real work takes place. The not so romantic and not so easy part of the craft, which is this: