The jealous man is so preoccupied with what he hasn't got that he fails to appreciate the value of what he has got. He loses the ability to feel glad because the sun is shining. He doesn't see the wonder and the newness of the beginning of spring.
We have enslaved the rest of the animal creation, and have treated our distant cousins in fur and feathers so badly that beyond doubt, if they were able to formulate a religion, they would depict the Devil in human form.
The fruit of the tree of knowledge always drives man from some paradise or other; and even the paradise of fools is not an unpleasant abode while it is habitable.