Once at the edge of a crowded Dublin sidewalk, I was waiting for the crosswalk. Just as the pedestrian light turned red, I started to step off the curb, intending to cross quickly before the traffic started. A tall man beside me put out his arm to stop me. His elbow grazed my shoulder. “The man who made time made plenty of it,” he said. I laughed, chastened with his Irish humor and forthright advice.

Turning 50 turned me both pensive and excited about time. We have plenty of it, yes.  But time i...