Maybe should add this to their book list?

The Dangerous Book for Boys
by Conn Iggulden, Hal Iggulden

to get it at Amazon:

A Native American elder once described his own inner struggles in this manner: "Inside of me there are two dogs. One of the dogs is mean and evil. The other dog is good. The mean dog fights the good dog all the time." When asked which dog wins, he reflected for a moment, "The one I feed the most."