Those who, either from their own engagements and hurry of business, or from indolence, or from conceit and vanity, have neglected looking out of themselves, as far as my experience and observation reach, have from that time not only ceased to advance, and improve in their performances, but have gone backward. They may be compared to men who have lived upon their principal, till they are reduced to beggary, and left without resources.

Seven Discourses Delivered in the Royal Academy (ed. 1778)