Oh, the dreaded E word!
I don't mean "electronic", which gives book publishers hives. No, I mean someone taking a hacksaw to your work and bleeding all over it until you're not sure you ever wrote anything good to begin with.
That said, editors have a thankless job. First, the writers come to them, whining and crying, "Oh please edit my work. It's good. It'll be worth your while; you'll see!" And then when they do as the writer asks, and edit to the best of their ability, the writers whine and cry, "Oh, how could you be so cruel? How could you kill my favorite sentences?" They get it coming and going.
The thing is, you can't edit your own work. You can see the story in your mind, but you're too close to it. You can't see where you've failed to explain it well enough or clearly enough through your writing. Worse, what about all the correctly spelled typos? The spellchecker won't catch it when you spell the darn word correctly, even if it's the wrong word. Taylor Mali gives an excellent illustration of why we need editors and proof readers in his poem The Impotence of Proofreading.
Having someone edit your work is nerve-wracking and scary, but the whole point of being a writer is so someone will eventually read your work! And not your mother, who's very proud of you and will tell you your writing is fabulous even when it's crap. Not your friends, either. They're too scared to hurt your feelings because they know this is "your baby".
You need editors and critique partners, people you can trust to tell you where your story needs elaboration, cutting back, or even rewriting. And you have to trust them to look at the story with your best interests at heart. They are there to help you make the story better. Granted, you don't want people who are derisive or so negative they kill your love and urge to write; but you do want people who critique seriously and with the intent to help you. The comments may be hard to read, but they are meant to make your story the best it can be.
The biggest thing you must do is let go of your "Attachment To The Words". You can't have favorite sentences when you hand off your work to an editor. They might get cut or moved or so rearranged they don't look like they did before they left your hands. You have to let it all go. Once it goes to your critique partners, it will change, probably for the better. The good news is you can choose which comments to take to heart and which to ignore. Maybe your reader didn't get what you were trying to say and a little rewording will help. Maybe they jumped the gun too early and the problem will be explained a little later, so you just need a little more setup to prime them.
A big thing to remember: the editor and critique partners are there TO HELP. The more comments they make, the more they care to make your story the best it can be.
I have (currently) four critique partners who help me smooth the rough spots, fill out the descriptions, and edit the crappy word choices I made. They also come from all walks of life: I managed to find a technical writing editor who can fix my word usage (YAY!); I found a scientific writer who enjoys science fiction and romance stories, and reads, a lot; I have a romantic suspense writer who has a great grasp of romantic elements in the crazy world of conflict; and I convinced a science fiction/fantasy writer to critique my work to help me with the paranormal aspects of my stories.
The more people who read your work and offer suggestions, the better. You'll never catch all the little quirks in your stories, but the cleaner you make them, the greater the likelihood you'll win a contract with a publisher and/or agent.
The biggest thing I want to offer: DON'T GIVE UP, even if you have a lot of work to do on the story you had critiqued. So this story wasn't the best; move on to the next one and learn from the mistakes on the first. Deb Coonts mentioned that the first story is good, the second story is great, and the third one is awesome, because she's had practice and learned from the mistakes. Same thing here. Don't give up after the first story if it isn't as good as you thought. The best stories are yet to come! :)