The laws of Nature teach us what we legitimately need. The sages tell us that no one is poor according to Nature; everyone is poor according to opinion. They then distinguish skillfully between desires that come from Nature and desires arising from our disordered imaginations. The desires that have limits come from Nature. The ones that run away from us and never have an end are our own. Poverty in material things is easy to cure; poverty of the soul, impossible.
Montaigne, Of Managing the Will (1580)
From The Practicing Stoic: A Philosophical User’s Manual by Ward Farnsworth
Bonus quote from the same book (Farnsworth’s own words):
The Stoic’s first observation about desire is that getting what we want tends not to produce the satisfaction that we imagined. It makes us want more. New desires appear when other ones are spent; our minds seem to have an appetite for desire itself, and for the illusion that fulfilling it will bring us to an endpoint. The end never arrives.