"Physical fitness is not only one of the most important keys to a healthy body, it is the basis of dynamic and creative intellectual activity.Intelligence and skill can only function at the peak of their capacity when the body is healthy and strong."

by John F. Kennedy

What this quote means is that you must never do anything that may hurt you or you body in emotional or physical way.One eaxample would be you well rested compared to you tired and sore.When you have rested you are fullof energy and is more likely to think bettter.In the other hand when you are tired an sore you don't feel like doing anything.Another example would be you doing you homework, you vs you+drug.When you are drug free you are able to think clearly work faster and smarter.When you are under the influence of a drug you aren't able to think as well and this will hurt you and your body later on causing permenent damage.