This is confirmed in Bhagavad-gītā (2.18) . Antavanta ime dehā nityasyoktāḥ śarīriṇaḥ: the body is perishable, but the soul within the body is imperishable. Therefore the duty of those advanced in knowledge in human society is to study the constitutional position of the imperishable soul and not waste the valuable time of human life in merely maintaining the body and not considering life’s real responsibility. Every human being should try to understand how the spirit soul can be happy and where he can attain an eternal, blissful life of knowledge. Human beings are meant to study these subject matters, not to be absorbed in caring for the temporary body, which is sure to change. No one knows whether he will receive a human body again; there is no guarantee, for according to one’s work one may get any body, from that of a demigod to that of a dog. In this regard, Śrīla Madhvācārya comments:

ahaṁ mamābhimānādi- tva-yathottham anityakam mahadādi yathotthaṁ ca nityā cāpi yathotthitā

asvatantraiva prakṛtiḥ sva-tantro nitya eva ca yathārtha-bhūtaś ca para eka eva janārdanaḥ

Only Janārdana, the Supreme Personality of Godhead, is ever existing, but His creation, the material world, is temporary. Therefore everyone who is captivated by the material energy and absorbed in thinking “I am this body, and everything belonging to this body is mine” is in illusion. One should think only of being eternally a part of Janārdana, and one’s endeavor in this material world, especially in this human form of life, should be to attain the association of Janārdana by going back home, back to Godhead.