When you edit, you imagine your enemy is seated on the other side of the table. Your enemy! And your enemy is going to read that with a viciousness, because he knows where you didn't work on it. He's going to shake it and really aim for that jugular. So you are going to polish, and revise, and rewrite, and cut out, and shape it, so that your enemy has no place to grip it. That's how you revise.