Robertson Davies:
I've always insisted on having a nap after lunch, and I inherited this from my father. And one time I said to him, "You know, you've done awfully well in the world. What do you attribute it to?" And he said, "Well, what drove me on to be my own boss was that the thing that I wanted most was to be able to have a nap every day after lunch." And I thought, What an extraordinary impulse to drive a man on! But it did, and he always had a twenty-minute sleep after lunch. And I'm the same. I think it is very important. If you will not permit yourself to be driven and flogged through life, you'll probably enjoy it more.
Quoted in Creativity, Csikszentmihalyi.