So writes Vicki Krueger on the Poynter website, which is a journalism blog, but I think her 9 points work well for novel writers as well. Point #3 is put it away (for a few minutes). Of course for novel writers, this should be much longer. I am always surprised how a couple week away from a manuscript can clarify ones writing.
I also heartily believe in reading out loud and from print vs off the computer or tablet. I always pick up more from reading print.