The lesson to be learned? Just this: our fatigue is often caused not by work, but by worry, frustration, and resentment. While writing this chapter, I went to see a revival of Jerome Kern's delightful musical comedy, Show Boat. Captain Andy, captain of the Cotton Blossom, says, in one of his philosophical interludes: "The lucky folks are the ones that get to do the things they enjoy doing." Such folks are lucky because they have more energy, more happiness, less worry, and less fatigue. Where your interests are, there is your energy also. Walking ten blocks with a nagging...