There are moments in life that divide everything into before and after. Some are dramatic. Others arrive quietly, carrying their meaning disguised as ordinary events. One morning in the late 1980s, I drove to work as I always had. I loved my job. I had become one of the pioneers in group fitness, traveling to California to study with the leaders in the field. I had discovered that the high-impact aerobics everyone was teaching didn't feel right in my own recently pregnant bod