That we just don't have what it takes to be a good leader.

Michael Roizen writes in the new book The Great Age Reboot: Cracking the Longevity Code for a Younger Tomorrow, 40 percent of premature deaths (premature meaning before you turn 75) are related to lifestyle choices.

If that sounds depressing, there's good news: Your choices can influence approximately 1,200 of the 1,500 genes that are switched "on," and likely influence the estimated 21,000 that are switched "off.".

One example Roizen cites is prostate cancer; after men improved their diet, level of physical activity, and ability to deal with stress, genes associated with prostate cancer growth switched off, while a gene that produces a protein causing cancer cells to self-destruct switched on.

The same applied to breast cancer: Lifestyle changes switched off genes that promote cancer and switched on genes that fight it.

As for longevity, every healthy thing you do helps turn off genes that cause you to age, and helps turns on "youth-promoting" genes.

The result is a virtuous cycle: Turning off bad genes and turning on good genes causes more bad genes to switch off and good genes to switch on.

The result is a genetic version of a growth mindset: Sure, genes are genes, but the choices we make influences how those genes function.

The key is to consistently -- not perfectly, but consistently -- make healthy choices that help prevent chronic disease and set you up for a long life.

Don't smoke.

Get a good night's sleep.

Regain and maintain a healthy level of LDL cholesterol.

Regain and maintain a healthy fasting blood glucose level.

Maintain a healthy weight for your height.

Most people use body mass index (BMI) to determine a "healthy" weight.

Your body fat percentage is probably a better indication of whether you're maintaining a healthy weight.

Roizen's target is to "sleep well and feel at ease in your own skin." I typically get eight hours, so I'm good on sleep.

But don't just think of sleep in terms of longevity; a 2018 study found that lack of sleep correlates with tension, anxiety, and lower overall mood?

Sleep is good for you later, and good for you now.

I don't smoke.

And don't smoke, and avoid second- and third-hand smoke as best you can.

I get plenty of sleep, and nature is right outside the door.

And, while it's nearly impossible to exercise your way to significant weight loss, or exercise enough to maintain a healthy weight regardless of what you eat, that likely contributes to my BMI as well as some of my test results.

You may get plenty of sleep, but spend significant time around people who smoke