I can edit my own work!
Editing Truth: You’re the worst person to edit your work.
Perhaps that truth is a little harsh, but what it comes down to is this: you know what you meant to say. No matter how many times you pore over what you wrote, your mind will fill in any gaps or ignore mistakes. The brain is an amazing thing. Because you know what you meant to say when you were writing, if there is a mistake or typo, your mind ignores it.
This is especially true for what they call function words (e.g., articles, prepositions) because these are not meaning rich words. There have been studies conducted on second language learners, and how they process function words versus content words (e.g., nouns, verbs). The results showed that learners focused on the content words because it is there that the meaning resides. Your brain will do the same, especially with your own work.
If you’re writing for an audience, you need to make sure that what you meant and what the reader understands are as closely aligned as possible. This is virtually impossible to do on your own because unless you can somehow manage to bring on a case of amnesia, you cannot separate yourself from your work.
About the only way to combat this particular problem is to leave what you wrote and come back to it after you have put it out of your mind for a while. But even that trick won’t solve everything. The best person to edit your work is someone else—after you’ve looked it over yourself.
Moral of the Story: You are the first line of defense for editing your own work, but depending solely on yourself could be your downfall.