We need to savor each moment, each accomplishment, each step along our life’s journey. A waiter remembers every detail of an order but forgets those details as soon as the plates hit the table. Inspired by this thought experiment, German psychologist Bluma Wulfovna Zeigarnik conducted a series of laboratory tests to demonstrate that people have a better recollection of the puzzles they are prevented from finishing than those they have completed. Evidently, our brains are wired to be preoccupied with the details of incomplete tasks. We have a deep-seated need to see things to the end. The human condition is...