By the time a piece of writing is finished, the pain and intensity of getting it completed can feel as if you'd just delivered a baby. As a result of the difficulty, your writing can feel like it's your baby. Guess what? It's not your baby. Everyone looks at his or her own baby (or grandchild) as if that child is destined for the cutest baby award. Way too many times, writers look at their own writing with that same starry-eyed look of wonderment.
Whether you are writing nonfiction or fiction, you need to be cold, cruel, and calloused with your writing. Hack it to pieces; then stuff it into a dark drawer to be left all alone for at least a week without even checking on it. After a minimum of several days, take your written piece out of the drawer and again, be cruel and calloused in your treatment of it. Editors don't have warm and fuzzy feelings for your writing, and neither should you. Your writing is not a baby to be coddled or handled with care. There are easy things to look for to see if your writing has been treated like a baby or been rough and tumbled through the editing process.
Read your writing aloud to hear how it sounds. If some of your phrasings sound so precious, so wonderful, so clever, it probably means they should be slashed from the total piece. You may think the writing is way too good to change, but you know that image of someone leaning over pretending to shove a finger towards the back of the throat? You don't want people doing that behind your back when they read something which might be nauseous purple prose.
Rhythm is important. Words should flow without bumpiness. Bumpiness can be caused by either difficult words to pronounce or by placing words adjacent to each other whose vowels or consonants stop the flow of pronunciation. The rhythm is also broken by too many words. In the movie Amadeus, the king, Emperor Joseph It, was evaluating Mozart's opera. Because of the king's allegiance to the musician, Antonio Salieri (who was later confined in an insane asylum from his intense jealousy of Mozart), the king responded to Mozart's music as "too many notes, just too many notes." Of course the king was wrong about Mozart's piece, but read your work to see if it might have too many words so that it loses the flow and loses the reader. A good example of too many words is when someone tries to tell a joke and goes on and on trying to extend the joke's funniness and the listener wants to yell, "Just get on with the joke!"
Do you write with vivid nouns and verbs? Look at this sentence as an example: The man drove the car down the road, through the fence, and off the edge. What visual picture did you get in your mind? Now don't change anything except use strong nouns and verbs: The assassin raced the Lexus down the freeway, through the railing, and off the cliff. Did you visualize anything different this time?
Two valuable books for learning how to edit your own work are Strunk and White's The Elements of Style and William Zinsser's On Writing Well. Both of these can help you write as a professional and not be someone who treats writing as a baby to be smothered with protection