When invoking that advice, check whether something really is a tradition!

This may be a good response to Zack's general approach, but if you apply it to Yvain's question, the conclusion is that Zack is not going far enough. Marriage is a very old and widespread tradition, while the imperative that everyone should graduate high school is extremely young, and schools themselves fairly young. Thus you should be much more willing to make marriage an imperative than school.