There is an excellent story done by NPR about a comic strip called “The Oatmeal” that explains why runners run. As the article says, it begins with a former fatty who is convinced that his fat is coming back. He has been running for hours on a terribly hot day in Japan. He is near exhaustion and is being chased by hornets, when he finds a vending machine where he drinks a purple, sugary drink, is revived, and continues his journey.
At the conclusion of this tail, we find out that runners run because it silences the blurches, krakens are slain, and demons are silenced. It brings them a sense of peace and is an accomplishment. I believe that this is true and enjoy running as well.