The best advice I've ever received on writing comes from my favorite Salinger piece Seymour: An Introduction. This is the most important passage I've ever read.
"When was writing ever your profession? It's never been anything but your religion ... Since it is your religion, do you know what you will be asked when you die? But let me tell you first what you won't be asked. You won't be asked if you were working on a wonderful. moving piece of writing when you died. You won't be asked if it was long or short, sad or funny, published or unpublished. You won't be asked if you were in good or bad form while you were working on it. You won't even be asked if it was the one piece of writing you would have been working on if you had known your time would be up when it was finished. I'm so sure you'll get asked only two questions. Were most of your stars out? Were you busy writing your heart out? If only you knew how easy it would be for you to say yes to both questions. If only you'd remember before ever you sit down to write that you've been a reader long before you were ever a writer... I think I'd give almost anything on earth to see you writing a something, an anything, a story, a poem, a tree, that was really and truly after your own heart."
Mr. Salinger, I'm eternally thankful.