There were two tigers; one lived in a cage and the other in the wild. The caged one didn't have to worry about his meal while the one outside was unrestrained.
The caged tiger was always envious of the freedom of the one in the wild, while the other one envied the caged one for his ease. One day, one tiger said to the other: "let's change places". The other one agreeded.
Thereupon the caged one went back to nature while the other came into the cage. But before long both died, one of starvation, and the other, melancholy.
Sometimes one is not conscious of his own happiness and always thinks the grass is always greener on the other side of the fence, but not think over that one man's meat is anoter man's poison.