When U.S. Marine Corp Officer Jake D.’s vehicle drove over an explosive device in Afghanistan, he looked down to see his legs almost completely severed below the knee. At that moment, he remembered a breathing exercise he had learned in a book for young officers. Thanks to that exercise, he was able to stay calm enough to check on his men, give orders to call for help, tourniquet his own legs, and remember to prop them up before falling unconscious. Later, he was told that had he not done so, he would have bled to death.