Abraham Heschel, a Jewish 20th century philosopher who died at 65 years of age, said (to paraphrase) the most profound characteristic we find ourselves left with as we age is "embarrassment." Hmmm. This actually ties in with many things discussed.
Hemingway the writer commented (again paraphrased) "life always surprises you with a left hook out of nowhere." This is somewhat related. We get blinded, or even are made to be the fool. After all our work, perseverance, and hardship, to find out we are the fool in life is, well, embarrassing.