I am more than halfway through a series of 12 Yoga classes. The brochure said it was for beginners. You’d think I would be getting the hang of it by now.

I’m not.

Our instructor is a willowy, 20-something, rubbery-limbed woman on stilts. She’s about six feet tall (five of those feet are her legs), and she weighs about 105 pounds wringing wet, including big jangly earrings. She doesn’t sweat.

She has long sleek dark hair wrapped up and pinned to the top of her head with something that looks like a spring-loaded clothespin, a dazzling smile, an aura of serenity and competence, and she can squat, sitting on her heels, indefinitely…