The ability to delay gratification as the most important determinant of success. // Dune by Frank Herbert states that the ability to endure pain to accomplish a greater goal is the way to judge whether a person is a human or an animal. Likewise this seems to say that the ability to not engage is pleasureable activities to accomplish a greater goal has a similar ability to classify. (Though it's not necessarily black and white.) Knowing these tools and knowing how to train people to be better is important.