One possibility is the disappointment of unrealized expectations. In our naïve twenties and thirties, our hopes are high, our scenarios rosy. Then reality trickled in like a slow leak in the roof. Only one person gets to be CEO—and it’s not going to be you. Some marriages crumble—and yours, sadly, is one of them. . . . Yet we don’t remain in the emotional basement for long, because over time we adjust our aspirations and later realize that life is pretty good. In short, we dip in the middle because we’re lousy forecasters. In youth, our expectations are too high.