In the system that I commend, men are freed, it is true, from the duty of sexual conjugal fidelity, but they have in exchange the duty of controlling jealousy. The good life cannot be lived without self-control, but it is better to control a restrictive and hostile emotion such as jealousy, rather than a generous and expansive emotion such as love. Conventional morality has erred, not in demanding self-control, but in demanding it in the wrong place.

Marriage and Morals (1929) by Betrand Russell