1. You can overwork things: knead bread that doesn't want to be kneaded and you'll have bread that only double-stomached animals can eat, because it needs to be chewed as cud. Kneading develops the gluten, you see, the long strands of protein that give the bread its structure and strength. But you don't want a bread to be all structure and strength. You want it to have softness too. Whatever process you use for your writing, leave room for softness, for mystery, for levity, for surprise.
2. Enjoy the process. There's plenty of good bread in the world already, and most of us can get some without fuss. So why make it? For the smell, for the feel in the hands, for the pure satisfaction. When I sold my first book I had a bad spell when I forgot that writing was fun, because now I was a Professional Writer (Of Very Little Brain). Remember: for the smell, for the feel in the hands, for the pure satisfaction.
3. Rising time is as important as kneading time. In bread baking, it's obvious, as it is not in writing. Some times the right work of the moment is not to work at all. Things need to sit and develop. Don't poke them. Be patient.
4. No writing is wasted. Did you know that sourdough from San Francisco is leavened partly by a bacteria called lactobacillus sanfrancisensis? It is native to the soil there, and does not do well elsewhere. But any kitchen can become an ecosystem. If you bake a lot, your kitchen will become a happy home to wild yeasts, and all your bread will taste better. Even a failed loaf is not wasted. Likewise, cheese makers wash the dairy floor with whey. Tomato gardeners compost with rotten tomatoes. No writing is wasted: the words you can't put in your book can be used to wash the floor, to live in the soil, to lurk around in the air. They will make the next words better.
(This is an excerpt from a much longer piece published a long time ago at Shrinking Violets, where I advise writers to stop reading writing advice. But I am trying to capture some wild yeasts to start a new culture and I remembered this and wanted to give it a little new life.)