I think of a pithy quote as a very short story. Such a short story can capture an important idea in a very few words, and such quotes tend to remain "fresh" over many years—and even over the centuries.
I have created two personal collections of such quotes for the IAE-pedia. See my general quotes at http://iae-pedia.org/Quotations_Collected_by_David_Moursund and my math education quotes at http://iae-pedia.org/Math_Education_Quotations. [These collections were revised and updated in March 2013.]