The business of a healthy eye is to see everything that is visible, not to demand no colour but green, for that merely marks a disordered vision. Likewise, hearing and scent, if healthy, should be alert for all kinds of sounds and odours, and a healthy stomach for all manner of meats, like a mill which accepts whatever grist it was fashioned to grind. In the same way, then, a healthy mind ought to be prepared for anything that may befall. A mind crying “O that my children may be spared,” or “O that the world might ring with praises of my every act,” is an eye craving for greenery, or a tooth craving for softness.

Marcus Aurelius