This is a post from staff writer Robert Brokamp of The Motley Fool. Robert is a Certified Financial Planner and the adviser for The Motley Fool’s Rule Your Retirement service.

I’ve always assumed that I’m screwed, longevity-wise. With a father and a grandfather who had heart attacks in their 60s and an uncle who had a stroke in his early 70s, I figured the genetic cards were stacked against me, at least when it comes to the odds of living a long life.

In fact, this is one of the reasons why I’ve decided to become much healthier over the past couple of years. But I couldn’t quantify it; I didn’t really know how much I was improving my chances for a longer life by eating better and exercising more. But now I know – or, at least as much as anyone can know such things.

In my last post, I discussed longevity since it’s an important variable in the calculation of how much you need to save to retire. The longer you’ll live, the more you need to save and/or work. Toward the end of my post, I linked to a life-estimating calculator on the website of Longevity Financial Consulting. Of course, no entity on Earth – be it a calculator, a doctor, or a crystal ball – knows exactly when you’ll die. The value of these calculators is that they illustrate which characteristics lengthen and shorten estimated longevity. As you answer each of the 35 questions, your projected life expectancy is adjusted, giving you an idea of how important each characteristic or behavior is to your longevity.

I’m sure many folks might take issue with the exact numbers. For example, being a female only added one year of longevity, as compared to being a male. That’s not enough for me to get a sex change. Plus, most actuarial studies I’ve read say that women live, on average, two to five years longer than men (the gap narrows as age increases). But my hunch is that the calculator has it right when it comes to which characteristics and behaviors are life-prolonging and life-shortening.

The good news for me is, I may not be as doomed as I thought. Here are how some of the highlights from my analysis.

At my current age (43), the calculator starts off assuming I’ll make it to 74. These are the factors that added years to my projected life:

  • A healthy diet (one year), including breakfast every day (another year)
  • Having a graduate degree (two years) – my master’s degree in education will finally pay off!
  • Regular, intense exercise (two years), which has resulted in an “athletic” weight/build (an additional two years)
  • I don’t smoke, which gives me four more years as compared to someone who smokes a pack a day
  • I rarely drink alcohol (one year)
  • I enjoy my job (one year)

Now, the factors that reduced my life expectancy:

  • My dad’s and grandfather’s coronary histories (three years)
  • The amount of miles I drive took away a year, but always using a seat belt added a year, so driving is a wash
  • The tool assumes six hours of sleep, which is about where I am, but I could add a year by getting eight hours of sleep
  • My anxiety and stress level, which can make me less happy (six years)

That last one was the real wake-up for me. I tend to be an “awfulizer” – I’m usually worried that something horrible will happen to my family, my job, the economy, or the world. I’m known at Motley Fool HQ for four things: 1) borderline inappropriate Halloween costumes, 2) giving away a CD of holiday songs each year, 3) dropping my pants in company meetings, and 4) being the most anxious person in the building. Of course, knowing that my stress level could shorten my life just makes me more anxious, which further reduces my life expectancy. It’s a self-reinforcing cycle. If I keep this up, I’ll die tomorrow.

Survey says…

Despite my sub-optimal attitude, the news from the longevity calculator is generally good: My life expectancy moved up to 83, so I’ve added almost a decade to my possible lifespan by choosing a healthy lifestyle. The calculator is kind enough to actually count the days I have left: 14,400. Finally, while I’m actually 43, I have a “Virtual Age” of 35, which either means I’m as healthy as a 35-year-old or that my online avatar looks 35.

The real takeaway for me is this: While I’ve been worrying that my family health history would shorten my life, all the worrying could actually be worse. I gotta work on that.

But I think I’m on the right track, especially with all the exercise. I’m not only concerned about the length of life, but also the quality. I know plenty of people who are in their 80s and even 90s, but many of them are not in decent enough health to enjoy it. Some of this just happens with age, but some of it is also the lifelong accumulation of unhealthy habits. Retirement will stink if you’re too sick or sore to enjoy it.

Fortunately, I do have a relative who is more like what I hope to be: my Aunt Joan, who is almost 81, rides her bike several miles at a time, after she wakes up before dawn to feed her cows, chickens, turkeys, and rabbits (that weigh 25 pounds each). I likely won’t have a farm in my 80s, but I hope to be just as active for as long as possible.

He looks relaxed. Add 6 years to his score.

Finally, as you begin to formulate your resolutions for 2013, perhaps the results of your own trip through the longevity calculator will provide some clues as to what you could work on – and a little extra motivation to work on it. Increasing the chances that you’ll live a few extra years might provide a jolt of motivation to eat better, exercise more, smoke and drink less, sleep more, and stop being so dang worried about everything.

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