When Colleen Haggerty lost her leg in an accident during her senior year of high school, she could have retreated from life and let her disability become her defining quality-and no one would have blamed her for it. Instead, she went the opposite way. In the years following her accident, Haggerty explored her physical world with vigor, testing the limits of her body by joining a ski team, playing with a co-ed soccer team, and taking up kayaking and...