Years ago, the philosopher Talbot Brewer was taking a yoga class in which the teacher noticed that many of the students were getting hung up on getting each pose exactly right. At one point, sensing how frustrated this fixation on perfecting the poses was making them, she said to the class, “Remember, the ends are the means to the ends.” The poses, in other words, aren’t really the point of doing yoga. Mastering the one-legged king pigeon or the revolved half moon is not ultimately what you’re there to achieve. You’re there to move your body, to break a sweat,...