What is play to one is death to another

There was a big pond in a certain village. It was filled to brim with water. Many frogs took their shelter in the pond. Some of them put their heads out of the water and croaked loudly. One day some naughty boys were playing by the side of the pond. When they heard the frogs croaking, some of them started to throw stones into the pond for fun. These stones hurt some of the frogs. All the frogs at once went down into water. But the boys did not leave the place. They remained standing there with stones in their hands. When the frogs raised their heads above the water, the boys started throwing stones again . As a result, most of the frogs became injured and died. So an old frog raised his head out of the water and said, "Dear boys, don't throw stones at us, please." "We're playing," said the boys, laughing. "I understand that" said the old frog. "But the stones you throw hit and hurt us. What's play to you is death to us."