The main job of rewriting a story is taking stuff out.
I think this also can apply to non-fiction too though.
The hardest. most difficult part is, of course, sitting down and doing the work, to begin with.
Overcoming resistance – as Pressfield would say.
But when you go back and look at what you have done, it can be like a puzzle of looking for what does not belong, and maybe adding a clarifying statement now and again.
I think some would argue that rewriting is when masterpieces are made.
Deletion is also the main task of writing a good email.
“When you write a story, you’re telling yourself the story,” he said. “When you rewrite, your main job is taking out all the things that are not the story.”
-Stephen King, On Writing