There is a nagging knowledge that you will always miss something, but you still have to make that effort. Spelling corrections, grammar changes, etc. -- those are bad enough. You can go over the work a dozen times and you'll still miss something. There is, however, something that most people don't often consider. Repetition of words and weasel words that sneak in because you stopped 'seeing' them. 'That' is a big one. Just and Only are two others.
Here is a lovely, free program to help you out. You can run it on the site or on your computer. I do the download version so I don't have to rely on my connection to get to it.
From the site:
Manuscript Analyzer 1.3a - This is a pretty unique tool for analyzing manuscripts. There are a number of programs that let you count the frequency of words in a document, but this takes it a step further and helps you identify junk phrases, "frequent offender" word patterns, and adverbs. It also lets you ignore common words that clutter up the high ranks of other word-counting programs, and allows you to focus on words by size.
I recommend this as a regular part of your editing. Take a chapter at a time and start weeding out and changing overused words, as well as hunting out those pesky adverbs you really don't need. However, also remember that adverbs exist for a reason. The trick, as with any of the words you find in these lists, is not to over use them.
Also, the program will list every word, including the and a. Those you can mostly ignore. I click on the frequent offender list until they come up to the top and start with that group. This can truly help create a cleaner, more readable story.
Don't go overboard and rework things until they're unwieldy to get rid of words, but do be aware of the ones you overuse!