Once upon a time . . . a dog managed to steal a large steak from a butcher's shop, and ran into the woods to eat it in peace. On reaching the banks of a stream, he happened to see his face reflected in the water. Never for a moment thinking that he was looking at himself in the water, what he thought he saw was another dog, holding a large steak in its mouth.
Being a greedy dog, he jumped into the stream to snatch the other dog's meat. Of course, the reflection vanished and he could see no sign of dog or steak.
Only then did he realize that, when he barked to frighten the other, he had dropped his stolen meat. Unluckily for him, the current was swift and the steak had been carried away. And though the dog hunted all over, he couldn't find a trace of it. Which meant, that instead of having two steaks. he was left with nothing.