The correction came when I walked into exercise class Thursday, and the instructor, the jolly British Maureen, said she noticed my posture as I walked toward the gym. “You’re leaning forward, ” she said. Of course I am, I think to myself. This is how I barrel through life.

“Pull your shoulders back, tilt your hips forward,” Maureen said. “Walk as if you have a pillow on your head.” So yesterday, as I did my three miles, I righted my shoulders, felt a plumb line stretch from my head to the sky. My chest filled with air. I felt taller and a little uneasy, as if I was on stilts. As if I was pretending.