In 1975, Salvatore Maddi, a psychologist at the University of Chicago, began to study the long-term impact of stress on employees at the Illinois Bell Telephone Company. It was supposed to be a simple longitudinal study. But in 1981, Congress passed the Telecommunications Competition and Deregulation Act, and the entire industry was disrupted. Within one year, Bell Telephone laid off half its workforce. Those who were left faced uncertainty, changing roles, and increased demands. As Maddi recalls, "One manager told me he had ten different supervisors in one year, and neither he nor they knew what they were supposed to do."

Some employees crashed and burned under the pressure, developing health problems and depression. Other employees thrived, finding a new sense of purpose and enhanced well-being. Because Maddi had been studying these employees for years, he began to search for clues in how they had responded to the stress.

A few things stood out about people who thrived under stress. First, they thought about stress differently. They saw it as a normal aspect of life, and they didn't believe that it was possible or even desirable to have an entirely comfortable, safe life. Instead, they viewed stress as an opportunity to grow. They also believed that difficult times required not isolating oneself. Finally, no matter what the circumstances, these "thrivers" believed we must continue making choices—ones that could change the situation or, if that wasn't possible, that could change how the situation affected them. People who held these attitudes were more likely to take action and to connect with others during stress.

Maddi named this collection of attitudes and coping strategies "hardiness," which he defined as the courage to grow from stress. Since that study of Bell Telephone employees, the benefits of hardiness have been documented across countless circumstances, including military deployment, immigration, living in poverty, battling cancer, and raising a child with autism, as well as in professions ranging from law enforcement and medicine to technology, education, and sports.