This essay is part of a column called The Wisdom Project by David Allan, editorial director of CNN Features. The series is on applying to one's life the wisdom and philosophy found everywhere, from ancient texts to pop culture. You can follow David at @davidgallan. Don't miss another Wisdom Project column; subscribe here.
(CNN)"Keep calm and carry on." "The only thing we have to fear is fear itself." "Don't worry, be happy."
These are the kinds of pithy, inspiring phrases and quotes that, historically speaking, have the power to steady us through challenging times. War. Depression. The 1980s.
Call them mantras, maxims or even memes -- they get repeated and recycled over the years, sometimes over the millennia, because they contain powerful jolts of easily accessible truth, insight and perspective.