Today's quote belongs to the most gifted artist (sculptor, painter, architect and poet) of the Renaissance, Michelangelo:
“A man paints with his brains and not with his hands.”
I think it summarizes what a Dungeon Master does as he prepares an adventure, or when, already around the gaming table, describes the scene as a group of weary adventurers arrives at a merry tavern, or sets the atmosphere as the party takes the first steps exploring some ominous ruins. Dungeonmastering it's like painting on an empty canvas.