The Crab and the Fox 螃蟹和狐狸

A crab once left the sea-shore and went and settled in a meadow some way inland, which looked very nice and green and seemed likely to be a good place to feed in. But a hungry fox came along and spied the crab and caught him. Just as he was going to be eaten up, the crab said, "This is just what I deserve, for I had no business to leave my natural home by the sea and settle here as though I belonged to the land."

Be content with your lot. 

有一次，一只螃蟹离开海边，定居在内陆的一块草地上，那里看着很美，有青青的绿草，是个养分充足的好地方。然而，一只饥饿的狐狸走过来，看见螃蟹并捉住了他。就在狐狸将要吃掉他之前，螃蟹说：“我真是活该，我没有理由要离开海边那个天然的家，像陆地栖息的动物一样，偏要到这里来定居。”

知足才能常乐。