The problem is that a lifetime doesn’t move at a constant speed. The older you are, the faster it goes, and you get the feeling that the end isn’t far away. To a young person, the phrase “the rest of my life” is something past a far-away horizon, very abstract and virtually endless. To an older person, the phrase “the rest of my life” could mean tomorrow or next month or next year . . . and it’s no longer a far-away horizon. And every time you look at a calendar, you feel that “your days are numbered.” So the older your get, you become more convinced that life is way shorter than it should be.