The first time I tapped-out during a fight, my Brazilian Jiu Jitsu coach, a purple belt, locked me in a triangle choke, controlling my movements like a lion chewing on a sofa cushion. As he cinched his legs around my neck, he levered my head into the meat of my shoulder which began constricting the blood flow from my carotid artery to my brain. I was folded and compacted and compressed indiscriminately, and before I reached out with my one free hand and tapped on his thigh to signal my defeat, I remember thinking: how could one person exert so much pressure?