Just like a madman, he forgets his relationship with the family. He loiters in the street. He eats anywhere and everywhere and all rubbish things. Although he may have a very rich father, well-to-do family, but forgetting.... Madness means forgetfulness of his real life. So we are now forgetful of our real life... So nirasih, now, to go to our original position, that is called tapasya. Tapasya means to revive our original normal life of Krsna consciousness. That is called tapasya. This tapasya is not possible by the cats and dogs or animals.Tapasya is meant for the human being.
Lecture on Bhagavad-gita 4.21, Bombay, 10 April, 1974