Gretchen Rubin’s Happiness Project books and blog, despite the saccharine appearance and self-helpy feel, rarely fail to yield some useful or enlightening wisdom. For example, her recent post about what she calls the “One-Coin Argument“.

She starts from a long-remembered footnote to the 16th century writing of Erasmus, explaining “the argument of the growing heap”:

“If ten coins are not enough to make a man rich, what if you add one coin? What if you add another? Finally, you will have to say that no one can be rich unless one coin can make him so.”

Which she goes on to put in perspective as follows:

I think the “argument of the growing heap” has stuck with me because it captures a paradox that I grapple with in my own life, and which is very significant to happiness: Often, when we consider our actions, it’s clear that any one instance of an action is almost meaningless, yet at the same time, a sum of those actions is very meaningful. Whether we focus on the single coin, or the growing heap, will shape our behavior.

Take going to the gym. You don’t feel like going to the gym, and you say to yourself, “What difference does one day make? It doesn’t matter if I skip today.”

True, any one visit to the gym is inconsequential, but the habit of going to the gym is invaluable. Does one visit to the gym make a person healthy? Ten visits? Eleven? Finally, you have to say that no one can be healthy unless one visit to the gym can make him or her so.