Change the format. If you’ve been writing and revising longhand, try working with a computer. Conversely, if you’ve been working with a computer, print out your document to revise longhand. Sometimes a shift this small can help. I have a theory that the extra time it takes me to write and edit longhand forces me to think a bit slower and find a slightly better sentence.
Enlist a reader. A second set of eyes views your writing from a different perspective. If you work on something on your own for too long, you start to lose sight of how a fresh reader might approach it. You may have edited out something crucial, the absence of which only a new reader can recognize. You also run the risk of editing the thing so thoroughly that it loses its original inspiration/spark/magic.
Sleep on it. If you hit a wall, set down your project and return to it later after you’ve slept. If you’re not sleepy, eat a meal or go for a walk.
Step away and do something enriching. Your body and mind need to recharge. It can help to do something that’s creative but lacks the pressure of writing/revising. Do something just for the joy of it. We can learn to bring joy and playfulness back to our writing. Revising then turns into a form of play. Moving a sentence to the end of a paragraph, or rearranging a scene, can be like drawing something in the sand, only for the image to be washed away. And we learn to stop making up imaginary consequences for “getting it wrong.”
Read. Your brain files away lesson after lesson all on its own. Reading from books can answer your revision questions, even if you’re unaware of what you’re looking for. We pick up stylistic tools and techniques, we develop our sense of linguistic rhythm, we even become better spellers when we read. And when we return to our writing, we do so with a more complete tool belt, with the ability to fix problems we couldn’t see before.