The Dog and the Reflection.

A Dog had got a piece of meat and was carrying it home in his mouth so that he could eat it in peace. Now, on his way home he had to cross a plank of wood lying across a running brook(小溪). As he crossed, he looked down and saw his reflection in the water beneath(在水底下). Thinking it was another dog with another piece of meat, he made up his mind to have that meat as well as his own. So, he tried to snatch(一把抓起) the tasty morsel(一块食物) from the reflection in the water, but as he opened his mouth, the piece of meat he had fell out of his mouth and dropped into the water, never to be seen again.

And, the moral is.

Beware, in case you lose something real while desiring an illusion.在你渴望幻觉中的东西时,却失去了真实的东西