Expressions of gratitude create in others an eagerness to reciprocate. When we become more fully aware that our success is due in large measure to the loyalty, helpfulness, and encouragement we have received from others, our desire grows to pass on similar gifts. Gratitude spurs us on to prove ourselves worthy of what others have done for us. The spirit of gratitude is a powerful energizer.
~ from THE ART OF CREATIVE THINKING by Wilfred Peterson