Editors! Who Needs Them?
Answer: writers! While I firmly believe writers must have the last word (so to speak) about what they write, they are too close to what they write to see it clearly and critically. I am a terrible proof-reader of my own work, partially because I read too fast and partially because my head knows what I thought I was saying, and what is actually on the page is just scanned with the unconscious assumption it matches this mental manuscript. But even more problematic than missing typos is thinking one is being clear when one is writing in a clumsy, confusing way. A good editor does more than just correct typos, spelling errors, and misleading punctuation. A good editor points out infelicities of usage and redundancies and all the other writing sins we overlook when reviewing our own work. (And resent having pointed out.)
Such good editors are hard to find, and even the best, most insightful, and tactful ones still tend to be viewed with hostility, for what writer is comfortable with being told some bit of assumed to be immortal prose or poetry is really shitty, careless writing? So the relationship inevitably is to some extent adversarial. A writer may greatly appreciate his or her editor, but conflict is inevitable.
Yes, good editors are hard to find, especially ones that are ‘on call’ 24/7 and have to put up with your fits of pique. I suggest marrying one. It worked for me.