A story in the Santi Parva of Mahabharata illustrates the importance of keeping the mind under control, said P.T. Seshadri in a discourse. There was a sage doing tapas in his ashram in the forest. There was a dog in the ashram, which adored the sage and never harmed anyone.
One day a leopard entered the ashram and wanted to kill the dog. Sensing this, the dog ran to the sage. The sage turned the dog into a leopard, so that it would not have to fear the intruder, and the two leopards became friends. Soon after, a tiger entered the ashram and the dog was again afraid. The sage turned the dog into a tiger. But, the dog changed its gentle ways and began to kill other animals. Then an elephant threatened the tiger and the dog which had become a tiger went back to the sage for help. He now turned it into an elephant, and it joined an elephant herd. One day a lion threatened the elephants and the dog went back to the sage and he turned it into a lion. But a sarabha came to the forest and the dog was again fearful. The sage turned it into a sarabha. The dog then thought, “This rishi changed me into many animals. What if he uses his power to turn some other animal into a sarabha? Then I will be challenged by that new sarabha. So it is best to kill the rishi.” The rishi could read the thoughts of the dog, and said, “You have no gratitude, although I helped you. So, I am going to turn you into a dog again.”
The story shows how the dog was not able to keep its svabhava intact, but kept changing. If a dog finds it so difficult to control its mind, how much more difficult it must be for humans to do so. The only option for us is to seek an Acharya, with whose help we can attain moksha. Acharyas are like a boat that helps a drowning man.
