Dean Karnazes has run most of the toughest endurance races in existence. He has completed 50 marathons in 50 days, won the Badwater race in Death Valley and ran 350 miles in just over 80 hours...without stopping.  Time Magazine named him one of the "Top 100 Most Influential People in the World." He's also a NYT Bestselling author. Among his books, Dean's most recent is "Ultramarathon Man: Confessions of an All-Night Runner." He's also written a book called "The Road to Sparta" regarding Dean's faithful re-creation of the run that the Athenian Pheidippides took from Athens to Sparta in 490 BCE. Mark and Dean  discuss the upcoming "300" ruck that Mark will do in September from Sparta to Thermopylae and get into the importance of mental toughness in ultra-endurance sports, and the preparation that goes into one of Dean's feats of endurance.  We all need to welcome greatness and use obstacles for our greatest successes.  Listen in to understand Dean's determination and mindset, and to be inspired.