You’ve probably heard a story or two about someone who lived past 100. Perhaps you have a wise-cracking great-grandfather. Or maybe you heard about that WWII veteran who ate ice cream and smoked cigars every day. According to a recent study, one secret to a long life might be wholly unrelated to what we eat or how much we exercise: our optimism.These stories tend to be both remarkable and slightly baffling. Sometimes, they defy our assumptions about what keeps people alive. What is their secret? Researchers examined long-term surveys of more than 69,000 women and 1,400 men. Both groups reported how optimistic they were: whether they expected good or bad things to happen to them in the future, and if they felt in control of important aspects of their life. The women averaged 70 years old and were followed for 10 years; the men averaged 62 years old and were followed for 30 …