There are some things I never imagined I’d say to my mother. “Because I said so.” “Stop yelling, or we’re leaving.” “No, you may not have dessert for dinner.” And yet, here I am—saying the kinds of things she once said to me, only now I’m saying them to her. When people talk about caring for aging parents, the stories tend to focus on the physical demands—medications, appointments, mobility. But what no one prepared me for was the emotional whiplash of parenting someone who once towered over me in strength, now lashing out like a tired toddler who skipped...