A philosophy of life, holding that people who do not look for an easy way of earning a living are foolish.

Alternative form of you could have fooled me

After being tricked once, one should learn from one's mistakes and avoid being tricked in the same way again.

It is easy to get money from foolish people. / It is difficult or unlikely that foolish people maintain their hold on acquired wealth.

There are consequences to not wearing a condom on one's penis

What you now tell me is true I thought was false, or I nonetheless think is false; I don't believe you.

A person who does not plan ahead and think matters through becomes involved in risky or unfavorable situations which prudent people avoid.

Foolish people repeatedly do foolish things.

(uncountable) The state of being foolish. / (countable) A thing or event that is foolish, or an absurdity.

(of a person, an action, etc.) Lacking good sense or judgement; unwise. / Resembling or characteristic of a fool.