Sometimes as writers we get bogged down in the process of writing, so much so that we may get stuck searching for the right word. Or phrase. Sure, we have been told (by Mark Twain) that the difference between the right word and the almost right word can is the difference between lightning and a lightning bug. But sometimes the energy expended to discover it may be too great.
So walk away. Take a break. Say, a stroll in the park or a trip to the refrigerator for something to drink. No time will be wasted, even if you decide to put your work away and come back tomorrow. Then you will be able to look at it with fresh eyes, because by then you would have cooled down and realized that good enough and still working is sometimes better than perfect and stumped.