By mile 10 of my first half-marathon, the persistent, frigid drizzle had forced my fingers into a clenched C shape. The thrill of running alongside thousands of people had mellowed into dull drive toward the finish line. Then, without warning or conscious effort, my body started moving faster. I was in the zone. In the 1960s, psychologist Abraham Maslow became the first academic to write about what he called "peak experiences," moments of elation that come from pushing ourselves in challenging tasks.