When Ragen Chastain sets a goal, she wants it to be nearly unattainable. Which is how she went from hating running to signing up for a marathon. “I decided I wanted to try a challenge and jump out of my comfort zone, and distance running had always been the thing that I was worse at in the entire world,” Chastain, 41, a speaker and writer, tells PEOPLE. “So I signed up for a marathon first thing.”