In any art, but especially in writing, you have to be totally possessed by it if you are to keep going in spite of any circumstances.
Neil Gaiman – Where do you get your ideas?.
Take a pencil to write with on aeroplanes. Pens leak. But if the pencil breaks, you can’t sharpen it on the plane, because you can’t take knives with you. Therefore: take two pencils.
Margaret Atwood’s Ten Rules for Writing Fiction « Aerogramme Writers’ Studio.