Most people are content to spend their lives achieving modest but realistic goals. They aim to rise towards the top of their business or to do well at the gym in the sport of their choice. And then there are the people who aim for more. These are the people who don’t just run marathons but are ultramarathoners, the people who don’t just walk regular buy actually walk around the world. What drives these people to do what they do? Maybe it’s an internal urge to be the best at something. Or maybe they’re just plain crazy.