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I remember when young the advice from parents and elders in China always was “learn a useful skill so that you can earn a living”. So engineering instead science became my college major. However, what I learned in four years of advanced engineering at MIT had little to do with my first job. Beyond some technical language ability and access to fundamental knowledge, such as elementary electricity, physics, and mathematics, the most useful skill that MIT taught me is the “ability to learn new stuff on my own”. My three years of work on digital circuitry, computers, and numerical control http://blog.sciencenet.cn/home.php?mod=space&uid=1565&do=blog&id=1121514 with titles to four patents were all learned on the job. When I returned to ph.d study once again what I learned in courses and ph.d thesis did not have that much to do with what I did to get tenure. Literally I had to create new results. There after every ten years for next four decades I started new field of investigation from game-theoretic control, to discrete event system, to perturbation analysis, to ordinal optimization – all of which I had to invent/discover and not learn from others or books. Thus, I am firmly convinced that beyond some basic knowledge on the language of mathematics, physics, and chemistry, it matters very little what subject you study in school. The only purpose of a university education is to enable you to learn new stuff on your own. The world is changing fast. There are “future shock” in every endeavor. To survive and even in retirement you must continuously learn new things even if they are not technical but useful thing to make retirement worry free.