"A dog with a piece of meat in his mouth was crossing a bridge over a stream. Looking down, the dog saw his own shadow in the water. Thinking that the reflection was a bigger dog with a piece of meat twice the size of his own, the greedy dog meant to have that, too.
Snarling, he opened his mouth to attack the enemy. At that moment his own meat fell onto the stream and floated away.
Now the dog realized at last that what he had seen was nothing but a shadow. Sadly, he said to himself, 'Grasp at the shadow and lose the substance.'" -From, "Aesop's Fables"