A few weeks ago, I was trying to stress to my macroeconomics class the distinction between nominal and real variables and why money is neutral in the long run. I said, "Real things matter." I realized that I was sounding like a self-help guru. Then, later that day in microeconomics, when I was trying to help them understand the concept of Nash equilibrium, I said, "You can only control you."
Maybe there's a book to written there: Economics for the Soul. It could include something about sunk costs, too ("You can't get back the past").
Copyright pending or something.