I feel like the Goose That Laid the Golden Egg is the classic in this genre.
A farmer and his wife wake up one day to find their goose has laid an egg of solid gold. The next day, they wake and find another golden egg.
This continues every day for months and brings them unimagineable wealth. They build a bigger house, buy a bigger herd of livestock, and dress themselves in finer garments. Soon, their goose is known around the country for its remarkable talent.
The farmer, now fully aware of the luxuries he had been missing out on, studied the goose with greed in his eyes. He figured that if the goose laid golden eggs every day, its innards must be filled with more gold than he could imagine.
Deciding that one measly golden egg a day wouldn’t be enough for much longer, the farmer took an axe to the goose, cleaving her in twain. As he dove into the goose’s innards to find the hidden gold, he realized quickly that this goose was the same as all other geese on the inside, and the goose that laid the golden egg was no more.
It’s short and you can’t miss the moral if you try. Aesop was writing that real shit.
I feel obligated to post this, despite the hate it will bring.