The Reedsy blog has 170 quotations on writing from famous writers.  Here are some of my favourites:

•  “You should write because you love the shape of stories and sentences and the creation of different words on a page. Writing comes from reading, and reading is the finest teacher of how to write.” — Annie Proulx
• “The greatest part of a writer’s time is spent in reading, in order to write; a man will turn over half a library to make one book.” — Samuel Johnson
• “Find a subject you care about and which you in your heart feel others should care about. It is this genuine caring, not your games with language, which will be the most compelling and seductive element in your style.” — Stephen King
• “Write what disturbs you, what you fear, what you have not been willing to speak about. Be willing to be split open.” — Natalie Goldberg
• “Sometimes the ideas just come to me. Other times I have to sweat and almost bleed to make ideas come. It’s a mysterious process, but I hope I never find out exactly how it works. I like a mystery, as you may have noticed.” — J.K. Rowling
•  “Your writing voice is the deepest possible reflection of who you are. The job of your voice is not to seduce or flatter or make well-shaped sentences. In your voice, your readers should be able to hear the contents of your mind, your heart, your soul.” — Meg Rosoff
• “There are some books that refuse to be written. They stand their ground year after year and will not be persuaded. It isn’t because the book is not there and worth being written — it is only because the right form of the story does not present itself. There is only one right form for a story and, if you fail to find that form, the story will not tell itself.” — Mark Twain
• “First, find out what your hero wants, then just follow him.” — Ray Bradbury
• “Get it down. Take chances. It may be bad, but it’s the only way you can do anything really good.” — William Faulkner
•  “Abandon the idea that you are ever going to finish. Lose track of the 400 pages and write just one page for each day, it helps. Then when it gets finished, you are always surprised.” — John Steinbeck
• “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
• “I would advise any beginning writer to write the first drafts as if no one else will ever read them — without a thought about publication — and only in the last draft to consider how the work will look from the outside.” — Anne Tyler
• “You don’t start out writing good stuff. You start out writing crap and thinking it’s good stuff, and then gradually you get better at it. That’s why I say one of the most valuable traits is persistence.” ― Octavia E. Butler
•  “It is worth mentioning, for future reference, that the creative power which bubbles so pleasantly in beginning a new book quiets down after a time, and one goes on more steadily. Doubts creep in. Then one becomes resigned. Determination not to give in, and the sense of an impending shape keep one at it more than anything.” — Virginia Woolf
• “When your story is ready for a rewrite, cut it to the bone. Get rid of every ounce of excess fat. This is going to hurt; revising a story down to the bare essentials is always a little like murdering children, but it must be done.” — Stephen King
• “People say, ‘What advice do you have for people who want to be writers?’ I say, they don’t really need advice, they know they want to be writers, and they’re gonna do it. Those people who know that they really want to do this and are cut out for it, they know it.” — R.L. Stine
• “Each writer is born with a repertory company in his head. Shakespeare has perhaps 20 players. I have 10 or so, and that’s a lot. As you get older, you become more skillful at casting them.” — Gore Vidal