Survivor’s guilt haunts Micah Herndon, widely hailed for a viral video (below) showing him crawling to the finish line this week at the Boston Marathon. The former Marine lost three of his best friends in a single day to IEDs when his column took part in the 2010 invasion of Marjah in Afghanistan. Every day he wonders why those men died and he lived. He knows there’ll never be an answer. Two of those men were fellow Marines, Mark Juarez and Matthew Bollard, riding in the same vehicle in which Herndon was the machine-gunner. He was knocked unconscious. They died. Another friend, Rupert Hamer, a British journalist accompanying the Marines, died the same day also from another IED.