Lewina O. Lee , Peter James, Emily Zevon and Laura D. Kubzansky:
Optimism is a psychological attribute characterized as the general expectation that good things will happen, or the belief that the future will be favorable because one can control important outcomes. Previous studies reported that more optimistic individuals are less likely to suffer from chronic diseases and die prematurely. Our results further suggest that optimism is specifically related to 11 to 15% longer life span, on average, and to greater odds of achieving “exceptional longevity,” that is, living to the age of 85 or beyond. These relations were independent of socioeconomic status, health conditions, depression, social integration, and health behaviors (e.g., smoking, diet, and alcohol use). Overall, findings suggest optimism may be an important psychosocial resource for extending life span in older adults.
You have to teach it young. From Daniel Kahneman in Thinking, Fast and Slow:
“If you are allowed one wish for your child, seriously consider wishing him or her optimism. Optimists are normally cheerful and happy, and therefore popular; they are resilient in adapting to failures and hardships, their chances of clinical depression are reduced, their immune system is stronger, they take better care of their health, they feel healthier than others and are in fact likely to live longer. Optimistic individuals play a disproportionate role in shaping our lives. Their decisions make a difference; they are the inventors, the entrepreneurs, the political and military leaders – not average people. They got to where they are by seeking challenges and taking risks. They are talented, and they have been lucky, almost certainly luckier than they acknowledge…the people who have the greatest influence on the lives of others are likely to be optimistic and overconfident, and to take more risks than they realize.”