I guess the “I” in that question should really be “we” because everyone needs an editor, even editors!
The issue is that after a while, we become blind to our work. Our eyes skip over the words because our brains know it so well. Having someone else read your work, especially aloud, will bring problems to the forefront really quickly.
I know it’s really hard to let someone see your work before it’s done. So, you don’t have to if that’s a real problem. You can keep working on it till you reach a point of comfort. There are, however, some key times that I really do recommend you hand it over.
I actually encourage writers to run their outlines (even in the most basic form) by someone – editor or fellow writer. Right at the very beginning, when you’re in the idea development stage, is a great time to seek guidance. We both know that your ideas aren’t fully fleshed out yet. But a good editor should be able to ask you enough basic questions about your ideas that you’ll be able to plot them in a way that makes sense. Especially for beginning writers, it’s easy to get caught up in one way of thinking about your ideas that you miss out on other perspectives. Sometimes, those other perspectives wouldn’t add anything to your work anyway. Regardless, the act of thinking about them ends up enriching your existing ideas and solidifying the path you take to building them out into a finished work.
Whenever you’re stuck and not quite sure where to take your idea next, put your work on the back burner; let it percolate in your mind for a while. (But not too long, especially if you have a deadline looming!). Then, if nothing’s coming to you, pass it on to an editor or fellow writer. That person should be able to ask you questions that will set your ideas in motion again. Together, you should come to see any gaping holes in the logic of your argument and any style problems.
So, finally, you’re at the point where you’re staring at your finished work. Now what? This is really the time to send it off to an editor. If you’ve been working with one all along, this final stage should be fairly painless. If not, you may find yourself going back over your work to make substantial changes.
Either way, look at the editing process as another step in the journey. All you’re doing is working with a buddy to find ways of expressing your great ideas to their maximum potential. An editor doesn’t sit in judgement of you or your ideas (or, at least, shouldn’t!). Instead, think of your editor as your sounding board.
Have fun with the process and let your creativity flow!