I used to collect quotes and write them in a little green book. I'm not sure why I stopped; I'm sure the little book is lying around my parents' house somewhere. Here are a few of my favorites about writing:
"The most essential gift for a good writer is a built-in, shockproof $#@! detector. This is the writer’s radar and all great writers have had it." Ernest Hemingway
"The worst enemy to creativity is self-doubt." Sylvia Plath
"Substitute 'damn' every time you're inclined to write 'very;' your editor will delete it and the writing will be just as it should be." Mark Twain
"The difference between the right word and the almost right word is the difference between lightning and a lightning bug." Mark Twain
"Writing is easy: All you do is sit staring at a blank sheet of paper until drops of blood form on your forehead." Gene Fowler
This last one rings especially true to me today. Sometimes I feel like I've chosen the most masochistic profession in the world. But then, every once in awhile, I'll get a day of absolute bliss from writing and there's nothing I'd rather be doing. I write for those days.