An nescis, mi fili, quantilla prudentia mundus regatur?
(Don't you know, my son, with how little wisdom the world is governed?)
This was supposedly written by the Swedish historical councellor Axel Oxienstierna in a letter to his son Johan in 1648.
Old men delight in giving good advice as a consolation for the fact that they can no longer provide bad examples.
François de La Rochefoucauld, Reflections; or Sentences and Moral Maxims (1665–1678), Maxim 93.
The hours of folly are measur'd by the clock, but of wisdom no clock can measure.
William Blake, The Marriage of Heaven and Hell (1790), Proverbs of Hell.