Why do you suffer yourself thus to be the sport of accidents, and your mind distracted by external objects, and not give yourself leisure to acquire any useful knowledge? and why do you live thus in a perpetual whirl of dissipation?

You will hardly find any man unhappy from being ignorant of what passes in the thoughts of other people; but he that does not attend to the regulation of his own thoughts, must necessarily be miserable.

Marcus Aurelius, Meditations