You're only as old as you feel

Age isn't just marked by the passage of time on a calendar. It's also a state of mind -- and while that may sound like a cliché, it's absolutely true that having a positive attitude can have a huge impact on aging.

Keep positive, and you can keep active and feel young even in your 70s, 80s, and beyond.

Act like an extra from "Grumpy Old Men," on the other hand, and you'll feel every bit your age and then some.

It's not just something I've seen in my own patients. It's a fact that's been confirmed by research, including a new study that finds seniors' attitudes and perceptions of aging can quickly turn into self-fulfilling prophecies.

Seniors who think of themselves as old and weak tend to withdraw, engaging in less activity and giving up things like exercise. They even spend less time socializing with friends.

On the other hand, seniors who have a positive attitude about aging are more likely to remain active and engaged, and more likely to keep socializing.

Granted, the study was based on just 29 seniors in one corner of the United Kingdom. But we've seen these types of results in other studies -- including one published just a few months ago that found seniors with a positive attitude about aging are 44 percent more likely to recover from severe disability.

But the best reason to stay positive isn't just to stay healthy and recover from disability -- it's because being positive can also help keep you alive. A Yale University study published nearly a decade ago found that a positive attitude adds 7.5 years to your life.

I don't know about you, but I think that's worth an attitude adjustment.