Lao Tzu had a knack for words of deep wisdom that sound childishly simple.
The quote come from chapter 46 of the Tao Te Ching:
When the Tao is present in the universe,
The horses haul manure.
When the Tao is absent from the universe,
War horses are bred outside the city.
There is no greater sin than desire,Laozi
No greater curse than discontent,
No greater misfortune than wanting something for oneself.
Therefore he who knows that enough is enough will always have enough.