That the most digestible way to teach ethics to humans is through narratives.

Another "not Aesop's fables" answer:

The story of the dog carrying a bone who looks in the water, and sees the reflection of another dog with a bone. He barks at this dog to try to take for himself a second bone, and in doing so, loses his own in the water. Trying to get more than you deserve or taking what others have leaves you with nothing of your own.

Under the category, "probably not actually from Aesop".

Hercules comes across a man with his cart in a ditch. The man is standing in the road, he asks Hercules for help. Hercules tells the man to get into the ditch, get his shoulder on the cart, push, and then ask for help.

Don't ask for help unless you've put some minimal effort into understanding the problem and trying to fix it yourself.

The one that's stuck with me throughout a lifetime is The Hare and the Tortoise (Project Gutenberg, safe click). Slow but steady wins the race.

Literally every fable ends with a good lesson, how to pick! The salt merchant's donkey sticks out as a memorable one because it's complex--the donkey's mistake is not trying to lighten its load, it is doing so excessively, trying to reduce its load to zero every day. The merchant's revenge seems somewhat cruel, but isn't actually forced upon the donkey until/unless, even though the sponges are very light on the last day, the donkey tries to make them even lighter by slipping into the water. It's a classic "pigs get fat, hogs get slaughtered" type message, but with some interesting nuance to it.

"Fuck around and find out." -The Boy Who Cried Wolf

I think the one that has stuck with me is the one about the man in the coat, and the sun & cloud competing to take his coat off. You get a lot further in life with kindness than through force

The scorpion and the frog.

People don't change their nature, they just learn to hide it better for the sake of public conformity.

The grasshopper and the ants - Don't be a lazy fuck and then expect others to bail you out due to your own lack of planning

The one about the crow adding pebbles to raise the water level in some vessel so that he can reach it. Problem solving!

Take the thorn out of the lion's paw, and don't charge him $10,000.

Not sure if it counts, but I quote The Donkey in the Lion's Skin all the time. Nobody has an infinite capacity to play a part. That isn't to say the reverse (over-applying expectations) isn't valid.

This is often compared to stories of Sun Wukong's tail and Zoroaster's encounter with Nebroel, both of which I cite as well.

The golden goose is timeless. Greed is a challenge in the best of times and for those of us living in deregulated capitalist hell, it can seem more like being a goose in a butcher shop. I constantly watch businesses squeeze in the short term to fail in the long term. Every quarter every day, people make the same, predictable greedy decisions and in the current system are often shielded from the consequences.