Sometimes you've had enough and you just need to go for a walk. It's understandable — a walk can clear the mind — and it's possible the extent to which your mind needs to be cleared should determine the length of the walk. There's no scientific evidence to support this, but the story of Emma Gatewood provides anecdotal evidence that this might be true.
Emma Gatewood — called "Grandma Gatewood" by her family and, later, the world — was one of the early thru-hikers of the Appalachian Trail (A.T.), the longest walking-only footpath in the world. When she left Ohio in 1955, she told her family she was going "for a walk in the woods," so it was surprising to her 11 children and 23 grandchildren that the 67-year-old matriarch of their family had undertaken the hike from Georgia to Maine on the 2,193-mile (3,529-kilometer) trail. They found out when one of them stumbled across a newspaper feature about their mother's trek.