I rowed in an eight-man shell in college. I grew up on the East Coast of the United States near a Chesapeake Bay estuary and was often on or near the water, so rowing was the perfect sport for me. 

At the end of my second season, we entered the largest crew competition in the US. After preliminary races, the boats were placed in very competitive heats that might be won by merely a few feet or even inches. 

It was the most exhausting race of my young career. I pushed myself harder than ever—so hard that for the last twenty or thirty seconds my vision went black. A quiet spiritual assurance that this would pass kept me rowing across the finish line. Within a minute or so, my vision did return. Still, this had never happened before; it was painful and frightening.