We are long before we are convinced that happiness is never to be found, and each believes it possessed by others, to keep alive the hope of obtaining it for himself.
 Samuel Johnson, The History of Rasselas, Prince of Abissinia (1759). copy citation

Context

““may by examining his own mind guess what passes in the minds of others. When you feel that your own gaiety is counterfeit, it may justly lead you to suspect that of your companions not to be sincere. Envy is commonly reciprocal. We are long before we are convinced that happiness is never to be found, and each believes it possessed by others, to keep alive the hope of obtaining it for himself. In the assembly where you passed the last night there appeared such sprightliness of air and volatility of fancy as might have suited beings of a higher order, formed to inhabit serener regions, inaccessible to care or sorrow;” source