Become a fan of h2g2
Running is an activity not dissimilar to walking, just a great deal faster.
Many people enjoy it as competitive sport, recreation or exercise, and say it is good for you. However the primary motivation for doing it is often a deeply felt masochistic spirit of self-hatred, or at least a personal guilt at not having said spirit.
It is one of those activities which seems to be unpleasant before, during and after. Several basic survival instincts need to be suppressed during the act of running for it to reach a satisfactory conclusion. However, once a certain level of fitness is attained, it is a very pleasant feeling to be able to climb the stairs or catch a bus without rupturing a lung or suffering a minor coronary.