You know how to write. You've been doing it since you were little. So why would you need some fancy-schmancy editor?
Imagine what might happen if you gave yourself a haircut. Sure, your hair would be shorter. It might not even look too bad, especially if you can ignore the back of your head. But after a day or so, you realize the haircut isn't quite the look you'd wanted. You probably end up going to a hairdresser to get it fixed.
Hiring an editor is something like going to the hairdresser to get the haircut repaired.
You've written a piece that you think is pretty good. You might even have thought about trying to get it published. Then someone suggests you send it to an editor. But why would you do that? Won't an editor change your precious words? Won't they make it into something that's no longer yours?
Just as the hairdresser who's fixing your haircut probably won't suggest purple dye to camouflage the messy cut, an editor's job isn't so much to change your work as to enhance it.
Sure, an editor can find mistakes in your work and help you fix them. But an editor can also point out spots where your meaning isn't clear, where you need to give your reader more (or less) information, where you're writing in generalizations, or too arcanely. [Ed's note: arcane refers to secret or inside information. Could you use a less obscure word here?]
Don't be afraid to explore the idea of hiring an editor. Especially if your words are venturing out into the realm of publication, you'll want your work [Ed: and your hair] looking as good as possible.