If you had the chance to reduce your risk of premature death by 50% by doing one thing, would you do it? What's it worth to you to increase the chances of seeing many of your goals and dreams come to fruition? How important is it for you to be around and hear your children say, "You know what... you were right about so many things?" You're working so hard now... don't you want to be able to be around and enjoy the spoils of your labor... or are you content to be one of the "richest people in the graveyard" as my friend Todd Musig says.
The one thing, of course, is exercise-being active. Thirty minutes of aerobic level exercise 3-4 times per week. The cost (other than missing that amazing repeat of a tv show or tearing yourself away from FB for a few moments) are minimal and the benefits beyond just longer life are amazing. If you need an example, check out the benefits of my choice of exercise-running-by reading this article from Runner's World.
Sure, anything could happen. But improving your chances by 50%? I'll take those odds any day.