Having certain traits or even tweaking your behavior to fake these traits could add years to your life, says Patrick Hill, PhD, psychology researcher at the University of Illinois. [sidebar]Here are three characteristics that may boost life expectancy:Your glass is half full. A study that analyzed 243 elderly people (average age: 97.6) found that most were more optimistic and easygoing than the general population. If your outlook could be sunnier, write down a few things you're grateful for daily. You're everyone's pal. Having strong social relationships can raise survival odds by 50%, found researchers from Brigham Young University. Not a social butterfly? Start small: Invite some pals to lunch, or consider starting a book club. You're never late. Conscientiousness (being detail oriented and responsible and always wanting to do a good job) is consistently associated with longevity, says Dr. Hill. Raise your conscientiousness by making (and using) to-do lists. More from Prevention: Surprising Signs You'll Live To Be 100