Jealousy in romance is like salt in food. A little can enhance the savor, but too much can spoil the pleasure and, under certain circumstances, can be life-threatening.
Wherever there is great property there is great inequality. For one very rich man there must be at least five hundred poor, and the affluence of the few supposes the indigence of the many. The affluence of the rich excites the indignation of the poor, who are often both driven by want, and prompted by envy, to invade his possessions.
There is a proper measure in all things, certain limits beyond which and short of which right is not to be found. Who so cultivates the golden mean avoids the poverty of a hovel and the envy of a palace.
Had the crow only fed without cawing she would have had more to eat, and much less of strife and envy to contend with. [To noise abroad our success is to invite envy and competition.]