I've spent the morning editing a couple of stories for submission.
What a nightmare!!!
I go through the text looking for errors in spelling and grammar and correct them. I change the odd word or phrase. I'm on the look out for any inconsistencies. Then I go through the whole process again and I might change something else. God help me if I go through it a third time because I guarantee that I'll find something else to tinker with.
When do I stop???
I think that if you keep going over a piece of writing there is always something that can be changed. It's hard to know when you are fiddling with something just for the sake of it.