New research is revealing that a certain kind of stress is good for us. Kelly McGonigal, a researcher at Stanford University, argues that challenges and difficulties aren't the real problem with stress. Sometimes life challenges actually reduce our stress levels. The real problem is what she calls "social isolation and social rejection."

For instance, a 2012 study in the Proceedings of the National Academy of Sciences found that high-ranking American government officials and military officers had lower cortisol (a hormone that measures stress levels) than a comparable group but who had little or no authority over others. The leaders had more burdens and challenges than burdened and challenged, got less nightly sleep, and were significantly more "stressed." However, according to the study, "Among the leaders, those who managed more people and had more authority also had lower cortisol levels and lower anxiety than those with less clout …"—and fewer challenges and burdens.

McGonigal says that many people may be trying to avoid this highly beneficial stress, believing it is harmful: "We know that having a meaningful job is protective … [and] we know that mastery of challenges is protective." McGonigal used to teach people how to manage, especially decrease, their stress levels. No more. She believes stressors like a challenging career, or managing a diversity of significant relationships, can give meaning, personal growth, and fulfillment in life. She summarizes, "In a way, stress is a kind of engagement with life."