I’VE HEARD SOME WONDERFUL EXPLANATIONS of mindfulness. Sylvia Boorstein, a writer and teacher, calls it “awake attention to what is happening inside and outside so we can respond from a place of wisdom.” The Vietnamese Zen teacher and poet Thich Nhat Hanh says, “I like to define mindfulness as the energy that helps us to be there one hundred percent; the energy of our true presence.” But my favorite definition comes from a fifth-grader at the Piedmont Avenue Elementary School in Oakland, California. The school offered a program of five weeks of mindful- ness training from a coach who visited classrooms twice a week, leading 15-minute sessions on how to have “gentle breaths and still bodies.” The students trained their attention by focusing on their breath and noting the emotions that arose. The coach also asked them to cultivate compassion by reflecting—“taking a moment”—before lashing out at someone on the playground. A reporter asked a boy participating in the program to describe mindfulness. “It’s not hitting someone in the mouth,” the 11-year-old said. His answer is wise …