Low expectations for a happy future might actually propel you into old age.
Compared with their counterparts with a sunnier outlook, older Germans who are more pessimistic tend to live longer, healthier lives, a group of researchers found.
"Our findings revealed that being overly optimistic in predicting a better future was associated with a greater risk of disability and death within the following decade," researcher Frieder R. Lang, of the University of Erlangen-Nuremberg in Germany, said in a statement. "Pessimism about the future may encourage people to live more carefully, taking health and safety precautions."
Lang's team looked at the 1993 to 2003 results of an annual German survey of tens of thousands of people, ages 18 to 96. These polls included information about the participants' health as well as their ratings of how satisfied they were with their lives and how satisfied they thought they would be in five years, on a scale of 0 to 10.
Among those 65 and older, 43 percent of the respondents had underestimated what their future life satisfaction would be five years after the initial survey, the researchers said. Thirty-two percent overestimated it and 25 percent had predicted accurately.
Each notch of overestimation was linked to a 9.5 percent increase in the chance a respondent would report a disability and a 10 percent increase in the chance the person would be dead five years later.
"Unexpectedly, we also found that stable and good health and income were associated with expecting a greater decline compared with those in poor health or with low incomes," Lang said. "Moreover, we found that higher income was related to a greater risk of disability."
Other contradictory studies suggest that the jury's still out on the secret to longevity and successful aging. Last year, a survey of about 1,000 older Americans found that a resilient attitude might trump good physical health in people's perception of how successfully they are aging. Another 2012 study of centenarians found that personality traits like being outgoing, optimistic and easygoing, as well as enjoying laughter and staying engaged in activities may be an important part of the longevity mix, possibly tied to genes.
The new findings were detailed online in the journal Psychology and Aging.
Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+.