“There is a difference, though, between savoring a moment and clinging to it. There’s no scientific upside to clinging, to mourning the last days of a great vacation. Acceptance of this requires practice, but to be a great traveler, to be a good student of life, as Bryant put it, you have to learn to let go. “One of the laws of travel,” he said, “one of the laws of the kingdom, is it must end.”