There is a link between positive emotions and better health outcomes, possibly mitigated through effects on the cardiovascular system. An optimistic explainatory style of life events may lead to a longer life. Danner et al (2001) analyzed the early-life autobiographies of women in the nun study and correlated them with health outcomes in a longitudinal manner. On average, 1.0% increases in the number of sentences expressing positive emotions led to 1.4% decreases in the hazard function of the Cox regression model (ie, the mortality rate). Stats are hard to do here, but look at page 8 of their study because they have a sick graph showing quartile rankings versus the probability of survival.
Danner DD, et al. 2001 Positive emotions in early life and longevity: Findings from the nun study. Personality Processes and Individual Differences. DOI: 10.1037//0022-35188.8.131.524.