Proverbs are meant to be short, pithy practical statements. Perhaps the most famous collection of proverbs come from the Hebrew Bible. But here, I have for you a proverb from a different source —
It's a wretched business to be digging a well just as thirst is coming over you.
— Plautus, Ancient Roman playwright (c. 250 - 184 B.C.E.)
Sources: Pickering, David, et al. The Facts on File Dictionary of Proverbs. United States, Facts On File, 2007. / Nixon, Paul, and Melo, Wolfgang David Cirilo de. Amphitryon. United Kingdom, Harvard University Press, 2011.