How do you edit your work? Do you write a paragraph and then go back and make changes? Or do you get to a halfway point in a story/essay, stop and go back to do a first edit? Or are you a writer who completes a first draft before starting to edit?
I prefer writing a complete first draft before doing any editing. Get the whole story written from beginning to middle to end. Then read through it once and put it away. Put it away? Yes, stash it in a file if you're composing on your computer. If writing in longhand, put the papers in a folder and out of your sight.
I can hear you say something like But I'm really into this now and I'd like to edit and send it out right away. Big mistake. You may have the skeleton of a story written but it's nowhere near ready to submit even though it might sound pretty good to you once you've written it.
Wait a few days, even a week, and then read through that first draft. I promise that you will see things that need reworking immediately, problems that you would probably have overlooked on the day that you wrote the draft. It's alright though. You've got the base and now is the time to revise and do a line by line edit.
After you do your editing, put the piece out of sight again for another day or two.Then look at it with an objective eye. Are you satisfied? Or do you still see places where you can make improvements?
How many times can a writer edit one piece of work? If you are such a perfectionist that you continue to edit over and over, you're liable to undo a lot of good that you did in that earlier first draft. How much editing is too much? That's hard to say but I'd say two, three times works well.
Have you ever watched a movie you liked again? Were there things in it that you missed on that initial viewing? I always get more out of a movie the second time I see it. Reading our initial draft and then the edited version is much the same.
Each time you edit, you see more that can be revised. Some writers want to add too much when they edit. Others are fearful of cutting. It makes me think of Goldilocks and The Three Bears story. You want to be like Baby Bear's porridge, chair and bed. They were just right for Miss Goldilocks. You want to get whatever you've written just right so take some time when editing. A rush job will not give you a polished product.