Ralph Waldo Emerson said this quote

That law of nature whereby everything climbs to higher platforms, and bodily vigor becomes mental and moral vigor. The bread he eats is first strength and animal spirits; it becomes, in higher laboratories, imagery and thought; and in still higher results, courage and endurance. This is the right compound interest; this is capital doubled, quadrupled, centupled; man raised to his highest power. The true thrift is always to spend on the higher plane; to invest and invest, with keener avarice, that he may spend in spiritual creation and not in augmenting animal existence.