AS LONG AS I KEPT MOVING, my grief streamed out behind me like a swimmer's long hair in water. I knew the weight was there but it didn't touch me. Only when I stopped did the slick, dark stuff of it come floating around my face, catching my arms and throat till I began to drown. So I just didn't stop. The substance of grief is not imaginary. It's as real as rope or the absence of air, and like both those things it can kill. My body understood there was no safe place for me to be.