The problem with writing something big--- like a novel, that is--- is that you have a carry case of "matter" wherever you go, and all sorts of impressions and ideas get collected in it, so that sometimes you feel tempted or even obliged to add all that stuff in your work.
It might present itself as an interesting possibility; only when you read through later or get a second opinion do you realise that you've been "hacking" into your own work through sly interpolation of peripheral detail. It takes such a long time, and you often get tired with words. If you read something really good in the meantime, there is a possibility that you can return fresh to your own work (without being too inspired by what you've read, hopefully). So the problem is Ideas & Words. I get into this obsession with words sometimes--- the sound and "feel" of a word; so much so that the meaning and the "fit" often suffer.
Freshness is all.
The word, its meaning and context have all to sharpen and live for you to be able to do the same for your reader. But when you're reading through large tracts of text you've written, you sometimes get fed up or alarmed or bored, and even good writing can appear stilted through over-reading. The best thing, I find, is to put it aside and return later.
But, still, re-reading is a must. Polishing your work when you're fresh is part of the craft. For me it is instinctual writing followed by craft. Which becomes the art! Having been a newspaper and magazine editor helps you to be precise and objective if not ruthless when confronted by favourite turns of phrases that don't really belong in your work. I have new writers sending me their work now and then to be evaluated, and the problem in most cases is that they've not read and re-read. And they just don't have it in them to cut out portions that don't belong.
Freshness is a mental state that is brought on by physical readiness. Walking, exercising and meeting people are "distractions" that become essential for a writer.
Which is why I wonder why I'm still sitting and staring into this screen day in and day out (sometimes, night-out too) ad losing all that freshness.