Now if life, without passion, must be altogether insipid and tiresome; let a man suppose that he has full power of modelling his own disposition, and let him deliberate what appetite or desire he would choose for the foundation of his happiness and enjoyment. Every affection, he would observe, when gratified by success, gives a satisfaction proportioned to its force and violence
 David Hume, An Enquiry Concerning the Principles of Morals (1751). copy citation

Context

“And it would be difficult to show why a man is more a loser by a generous action, than by any other method of expense; since the utmost which he can attain by the most elaborate selfishness, is the indulgence of some affection. Now if life, without passion, must be altogether insipid and tiresome; let a man suppose that he has full power of modelling his own disposition, and let him deliberate what appetite or desire he would choose for the foundation of his happiness and enjoyment. Every affection, he would observe, when gratified by success, gives a satisfaction proportioned to its force and violence; but besides this advantage, common to all, the immediate feeling of benevolence and friendship, humanity and kindness, is sweet, smooth, tender, and agreeable, independent of all fortune and accidents.” source