I’ve never run a marathon—never put 26.2 miles together consecutively. I haven’t even run a half-marathon or registered for a 5K.

In the United States, about 450,000 people per year run a marathon. Next January, I’ll be one of them.

A lot of people say it’s crazy. I can’t disagree, but let me really tell you about crazy. Courtesy of my good friend Matt Galli, I recently read Ultramarathon Man: Confessions of an All-Night Runner. The book is an autobiography by Dean Karnazes, a relatively ordinary guy with an unbelievable passion for running. Karno (as he is affectionately dubbed by his friends) tells his story of transforming from a regular, 8-to-5-Corporate-America citizen into the Ultramarathon Man.

He details his life and how running came to consume it. It’s an inspiring tale about overcoming rational limits in an effort to physically and mentally push yourself beyond what you could ever imagine. The book has encouraged me tremendously in my running life and has challenged my thinking on a lot of things–most notably pain.

Pain and suffering are often the catalysts for life’s most profound lessons.

Dean doesn’t run to win competitions (although he’s won the toughest race in the world). He doesn’t run for the fame or the glory (as there’s not much to be had in ultra endurance sports). He doesn’t run for the money. He runs in memory of his sister Pary. He runs to see how far he can push himself beyond the theoretical limits of the human body. He runs to help people.

Dean runs ultramarathons (any distance over 26.2 miles). He’s run: 135 miles through Death Valley in 120-degree temperatures, a 200-mile relay by himself, and 350 miles without sleep. He was the first person to run a marathon on the South Pole. He’s run 50 marathons in 50 states in 50 consecutive days—and he’s no different than you or me.

I wasn’t born with any innate talent. I’ve never been naturally gifted at anything; I always had to work at it. The only way I knew to succeed was to try harder than anyone else.

It hurts me just as bad as anyone else. I’ve just learned an essential insight: your legs can only carry you so far. Running great distances is mostly down with your head..and your heart.

If you’re a runner looking for some extra motivation, or if you just want to push beyond the ordinary in your own life, pick up Ultramarthon Man.

If you’re not pushing yourself beyond the comfort zone, if you’re not constantly demanding more from yourself—expanding and learning as you go—you’re choosing a numb existence. You’re denying yourself an extraordinary trip.