"In any culture, the development of self-control is crucial. This ability, which depends on the prefrontal cortex, provides the basis for mental flexibility, social skills and discipline. It predicts success in education, career and marriage. Indeed, childhood self-control is twice as important as intelligence in predicting academic achievement." Read more from this excellent NYTimes article, "Building Self-Control, The American Way."
Also, click on a related previous blog post "Marshmallow Test."