Every writer should go over their own work – more than once. But there comes a point in the process when you can no longer look honestly and objectively at the text in front of you.
When I finished editing my master’s thesis in London, and I felt it was as good as I could make it, I sent it to someone, to have them read it. When it came back, I realized I was missing complete sentences. Not just words – entire sentences.
I knew exactly what I was trying to say, and so when I read it, I wasn’t reading the words on the page. I was reading what should have been there. My brain was filling in the gaps.
If I hadn’t had that person read it, I would have turned in something that in no way represented what I meant. That’s just one example of how having someone else read your work is incredibly beneficial.
There comes a time when it’s just too familiar to you. It all makes sense to you. You can no longer see the flaws. That’s when a beta reader or a professional editor can really help. They’re approaching it completely openly and honestly, and they’re going to pick up things that you would never have noticed, because it all makes sense to you.