My baby recently left home. He’s 19 and launching his life in an age-appropriate way: subsidized by his parents, at school in a distant city, directing himself toward self-sufficiency and maturity. Nevertheless, the day his move became effective, I felt like I’d left him alone in the woods with no pebbles. This tender son was born 16 years after his big sister. She was learning quadratic equations as he was learning how to hold a spoon. When either child faltered, I’d try to help: “Here, let me.”