Knowing One's Limits

Nicolas de Chamfort, tr. William G. Hutchison, in: The Cynic's Breviary, 1902:

“Are you not ashamed to wish to speak better than you can?” said Seneca to one of his sons who could not work out the exordium of an oration he was composing. One might say the same to those who adopt principles stronger than their character will bear. “Are you not ashamed of wishing to be more of a philosopher than you can be?”