" It was clear from talking to them, that what kept them motivated was the quality of the experience they felt when they were involved with the activity. The feeling didn’t come when they were relaxing, when they were taking drugs or alcohol, or when they were consuming the expensive privileges of wealth. Rather, it often involved painful, risky, difficult activities that stretched the person’s capacity and involved an element of novelty and discovery. "

― Steven Kotler , The Rise of Superman: Decoding the Science of Ultimate Human Performance