Oh, what? An editor saying you can self-edit? Don’t get too excited. You can do it, and you should do it, but you should not be the last person to do it. That said, there are some pretty standard steps involved when reviewing your work before you send it out into the world (or even to an editor!).
The goal of any editor is to bring out the strongest version of the text in front of us, no matter what stage it’s at. We are ever-so-careful of the suggestions and comments we make as we strive for better understanding of the material and its design. You have a goal in mind for this work and we’re the intermediary who helps you reach your target audience the most effectively.