Caffeine comes in many forms, either through coffee bean, tea leaves or even as a chemical extract - caffeine can be used to push your workout to the next level without the side effects of traditional stimulants.
Many studies have even shown caffeine to be a very effective substance to help prolong life and lead to healthier states of body composition.
Running provides a deep sense of euphoria. Going on a run can stimulate a happy sensation in your brain similar to the effects of drugs. This is why some runners will report they run for the high, never stopping until their legs give out.
The urge to run further, run faster and train harder can consume you - to the point where running becomes a big part of your lifestyle. Trust us, this is not a bad thing.