It's no big revelation to say that discipline, delayed gratification, pays off. But compared to intelligence, how well does it correlate with academic success? More closely than you might think. In a study of middle school students:
Both IQ and self-discipline are correlated with GPA, butself-discipline is a much more important contributor: those with low self-discipline have substantially lower grades than those with low IQs, and high-discipline students have much better grades than high-IQ students. Even after adjusting for the student's grades during the first marking period of the year, students with higher self-discipline still had higher grades at the end of the year. The same could not be said for IQ. Further, the study found no correlation between IQ and self-discipline—these two traits varied independently.