A modern version of this maxim is “Keep it short and simple.” A maxim is a saying about a general rule of life. Two synonyms for “maxim” are “proverb” and “aphorism.”

Example:  “Jake was trying his best to get me to invest in his banking scheme before the rates went up, citing the old maxim ‘he who hesitates is lost’, but I didn’t trust his calculations, and decided to keep my money in mutual funds.”