Psychologists at Duke University have found that enormous success is healthy only for people with self-esteem to

For someone struggling with a poor self-image, hitting a ball out of the park may tax the immune system,
helping the body to spiral into disease. Instead, the Duke scientists
say, the Brians among us stay healthier when success is more modest.

The Duke research is just one example of a new paradigm in
psychoneuroimmunology, the study of the links among emotion, immunity
and the brain. Although we’ve long equated positive emotion with health
and negative emotion with illness, recent studies add nuance and
subtlety to these broad ideas, proving them just partially correct and
in many cases wrong. Among the surprising findings: Stress can prime
the immune system, making us stronger.

Read about the study in a Fort Worth Star-Telegram article.