The conflict of the literal meaning and the metaphoric is where the comedy comes from. “Keep your feet on the ground” is the sort of thing one expects to see on an office-wall inspirational poster with a picture of a mountain or a tree. The logistical difficulties of such a position are not expected, and the unexpected is funny.
“Confucius say, man who keep feet on ground have trouble putting on pants”
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At least in the U.S., a man who “keeps his feet on the ground” is metaphorically emotionally grounded, sure footed, and not easy to shake up. The ‘saying’ is a play on that metaphor, suggesting that being too stable can be its own kind of handicap. Alternatively, the ‘saying’ is just being silly.
Confucius say “Man with hole in pocket feel cocky all day.”
Confucius say “Virginity is like a bubble. One prick, all gone.”
Confucius say “Learn to masturbate - come in handy.”
Confucius say “Man who sit on thumbtack will get the point.”
Confucius say “Man who buy many prunes get good run for his money.”
Confucius say “Man who laughs last does not get joke.”
Confucius say, “The way of the superior man is threefold, but I am not equal to it. Virtuous, he is free from anxieties; wise, he is free from perplexities; bold, he is free from fear.”
More metaphorically, perfect stability also means you’ll never accomplish anything, since some expenditure (and thus risk) is necessary to get a return.
Confucius say “Posters who overthink lame joke, waste … uh, time.”
It wasn’t one of his best.
Haven’t you ever heard the phrase ‘making time’ used to connote making out? He’s saying they’ll be in bed the whole time, or at least very pleasantly indisposed.
Well possibly - but the ‘make hole weak’ is far more inkeeping with the style - and funnier (given that your definition is pretty obvious, and the humour is in reading the second meaning).