The most foolish fail because of not thinking things through at all. The less but still foolish think about their lives and goals but lose focus and easily get distracted by the superficial but flashy, by the unimportant but entertaining. The wise quickly recognize the consequential, see which courses of action lead to gain and which to loss, and prioritize their most diligent concentration and highest skill to the most important issues. For most however, "common sense is not so common" and they never lose their common sense because they didn't have any to lose. They make a big deal about things that don't matter and ignore the most important issues. The wise apprehend life's hidden and obscure treasures, deeply root them in their minds, and apply their most diligent and focused attention.