Sy Safransky has this to say about editing:

Readers sometimes ask how much I edit my own writing.

I edit until each paragraph has lost the ten pounds it gained over the winter.

I edit until each sentence can survive three days in the wilderness on its own.

My father taught me to look at a sentence and, if it didn’t deserve to live, shoot it between the eyes. 

Sy Safransky, The Sun Magazine, May 2011