acquaintance, n.: A person whom we know well enough to borrow from, but not well enough to lend to. Ambrose Bierce
Science is what we understand well enough to explain to a computer. Art is everything else we do. Donald Knuth
While it is well enough to leave footprints on the sands of time, it is even more important to make sure they point in a commendable direction. James Branch Cabell
He keeps his road well enough who gets rid of bad company. Portuguese Proverb
Prepare the fallow field well enough and you'll be free to go off and gather the hemp ties. Sicilian Proverb
Leave well enough alone. American Proverb