They say familiarity breeds contempt. This may not be true of writing, but it is true that familiarity breeds all sorts of problems.
Yes, it can be a problem when you know your writing backwards and forwards. Being objective is the best way to make your revisions effective—it means you can honestly point out flaws and delete those dear little scenes that you love but really serve no use. But being too familiar with your work creates a bias, and that makes it hard for you to polish your prose.
This happens a lot in revisions. People like me tend to write their novels without looking back. But when it comes to revision, my methods require reading and rereading and rereading yet again. With all that reading, I practically memorize the important parts of my story. With The War Horn alone, I've completely rewritten the opening pages three or four times, in addition to rereading them dozens of times.
It's a problem. Your eyes get all glazed over, and your mind starts skipping ahead because you've read it all before. As a result, you miss out on a missing word here or there, or a structural problem, or a bad spot of passive voice.
Recently I had this problem with my Will Vullerman revisions. One story in particular has given me some trouble, and as a result I've reread it as many as ten times in the last two weeks, in addition to rewriting half a dozen key scenes.
Luckily, I'm coming back to the stories after nearly a year and a half of letting them sit on the shelf. Because of that, the first time I reread them, the stories were fresh. And since these are the final revisions, this familiarity isn't as much of a problem.
But when familiarity gets really bad, I suggest doing one of several things.
One, it's a good idea to leave your story on the shelf for a while. Don't use this as an excuse for procrastination, but also recognize your limits. Giving your story some space allows you to be fresh and critical when you do happen to pick it up again.
Never underestimate the power of a long hiatus. After taking a long break from Tornado C back in 2012 (long before completion) I reread the first six chapters several months later. Guess what? The story had a gravity and power that took me by surprise. It was actually good!
I'm currently taking the hiatus approach for my Tornado C revisions. I finished it last October and I haven't touched it since. I'm taking it slow; hopefully, come March, I'll pick it up again and revise it nonstop till August. (Being my biggest novel at 90,000 words, it seems appropriate to go slow and steady. There are few things worse than rushed revisions.)
Two, try printing it out or putting it on an e-reader. I did this for my Will Vullerman story; seeing it on my Kindle allowed me to see a lot of technical mistakes that I had overlooked on my computer screen.
Three, read it out loud and see what happens. You can read it to yourself or to somebody else, whatever works. You'll be surprised at how many mistakes and awkward phrases you'll find! Badly constructed sentences will jump out at you like the stroke of a red pen. (It's always awkward when this happens to you when you're reading it aloud—to a critique group. Oops!)
Fourth, send the story off to other people to read. Sure, that doesn't solve your own familiarity problem, but a great critique is worth a dozen of your own revisions. It'll allow you to revise your blind spots.
And, of course, there's always the possibility that you should stop revising altogether. Sometimes enough is enough. Your story will never be perfect, although perfection should always be your goal. Eventually you'll have to let it go and declare it finished.
Whatever happens, try your best to view your writing from the reader's point of view. That's the most important thing, in the end!