"Moderation in all things."
I'm a strong believer in education, and credit my education (both supervised and on my own) to my level of success today. But there is such a thing as going too far.
My mother was absolutely anal about education taking priority over everything, no exceptions. I was also forbidden to get a job as a minor, because it might take away a second of time from my formal studies. The result was that I was forced to miss important family events, including my grandfather's funeral (we were very close), and my first ventures into the working world were really bad.
I had the privilege of being able to work at a place that hired high school students and got to see how valuable an experience it was for these kids to get real work experience sooner than later. Most of those kids went on to college, and I'll bet that their high school work study gave them an edge over other college graduates. I can say with certainty that my job experiences as a young adult before and during college prepared me for the real world of business.