The Yale study claims that a good attitude helps keep your heart pumping and your feet tapping an additional 7.6 years on average. An optimistic outlook adds more years to your life than low blood pressure (4 years or less), low cholesterol (4 years or less), a healthy weight (1 to 3 years) and regular exercise (1 to 3 years).
Think about how much you hear about improving your health by losing weight, and compare that to how much you hear about crushing your own pessimism to improve your health.
The good news is that you can deliberately become more optimistic, and not by becoming a pie-in-the-sky airhead. Real optimism does not include fooling yourself. In fact, it is just the opposite. To become more optimistic (in the scientific sense of the word), you need to look at your pessimistic thoughts and find out if you've made any mistakes in your thinking, and then correct them. The method is simple and straightforward, and works very well.
So rather than becoming more "positive" by selectively ignoring some negative aspects of reality, real optimism includes fully facing all of reality, and not allowing your mind to interpret reality more negatively than is justified by the facts.
To learn more about crushing your own pessimism, start here: Undemoralize Yourself.
If you have already learned enough to feel confident in optimism's powerful advantages, and would like to help someone you know become more optimistic, try a little motivation. Sharing findings like the Yale study is a great way to begin.