Once, toward the end of her life, when she was not in good health, I woke my mother up from a nap, and, unusually for her, she snapped fully awake immediately. Over the next several minutes, she talked at length about the strict Catholic schools she had attended as a girl, remembering how mean the nuns had been and how afraid she had been of them. Her memories were vivid, and I was surprised that she had never shared them with me before.

The reason she hadn’t shared them with...