A mouse was in constant distress because of its fear of the cat. A magician took pity on it and turned it into a cat. But then it became afraid of the dog.
So the magician turned it into a dog. Then it began to fear the panther, so the magician turned it into a panther. Whereupon it was full of fear for the hunter.
At this point, the magician gave up. He turned it into a mouse again saying, “Nothing I do for you is going to be of any help because you have the heart of a mouse.”
This is from The Heart of the Enlightened, a book of spiritual stories by Anthony de Mello.