Of all the passions, jealousy is that which exacts the hardest service, and pays the bitterest wages. Its service is to watch the success of one's enemy; its wages to be sure of it.
Jealousy is sustained as often by pride as by affection.
Love may exist without jealousy, although this is rare: but jealousy may exist without love, and this is common; for jealousy can feed on that which is bitter no less than on that which is sweet, and is sustained by pride as often as by affection.