I love looking up quotes about writing, and the internet makes it so easy. The following are quotes I've found on a couple different sites, which of course I'll reference, with thanks to the people who put their wonderful collections of writing quotes together.
Writing Inspirations and Affirmations...
The test of literature is, I suppose, whether we ourselves live more intensely for the reading of it. ~Elizabeth Drew
Writing is the only thing that, when I do it, I don't feel I should be doing something else. ~Gloria Steinhem
Writing is a solitary occupation. Family, friends, and society are the natural enemies of the writer. He must be alone, uninterrupted, and slightly savage if he is to sustain and complete an undertaking. ~ Jessamyn West
I don't wait for moods. You accomplish nothing if you do that. Your mind must know it has got to get down to work. ~Pearl S. Buck
Fill your paper with the breathings of your heart... ~William Wordsworth
The above from http://www.wisdomquotes.com/cat_writingwriters.html
"Writing is the hardest work in the world. I have been a bricklayer and a truck driver, and I tell you -- as if you haven't been told a million times already -- that writing is harder. Lonelier. And nobler and more enriching." ~Harlan Ellison
"Success is a finished book, a stack of pages each of which is filled with words. If you reach that point, you have won a victory over yourself no less impressive than sailing single-handed around the world." ~Tom Clancy
"Good writing is supposed to evoke sensation in the reader--not the fact that it is raining, but the feeling of being rained upon." ~E.L. Doctorow
"I write for the same reason I breathe -- because if I didn't, I would die." ~Isaac Asimov
"The strokes of the pen need deliberation as much as the sword needs swiftness." ~Julia Ward Howe
"The great art of writing is knowing when to stop." ~Josh Billings
The above came from: http://www.heart4teens.com/writer_s_quotes