Supreme Lord Śrī Krishna and the jīvas are eternally related with each other. Lord Śrī Chaitanya Mahaprabhu has termed this relation as acintya-bhedābheda. This means we are different and simultaneously non-different from Supreme Lord Śrī Krishna.

When I was at home I had several doubts about jīva-tattva, bhagavad-tattva, etc., in my mind and I used to write letters to my Most Revered Śrīla Gurudev. One time Śrīla Gurudev asked me to read Jaiva-dharma, written by Śrīla Bhaktivinode Thakur. I went to a library and got that book. When the book was issued to me, the librarian said, “You are the first person who has asked for this book. So far no one has got this book issued.” When I read Jaiva-dharma, all my doubts about jīva-tattva and bhagavad-tattva were clarified. You may also read Jaiva-dharma. You will get all the answers to your questions because Śrīla Bhaktivinode Thakur is not an ordinary human being. He is Śrī Kamala Manjari in Goloka-līlā.

Human birth is very rare

The jīvas here means all the living entities including beasts and birds. There are 8,400,000 kinds of living entities. In Viṣṇu Purāṇa it is said:

jalajā nava lakṣāni sthāvarā lakṣa viṁśati
krmayo rudra-sankhyakah pakṣinām daśa lakṣaṇam
trimsal lakṣāni paśavah catur lakṣāni mānusah

There are 900,000 kinds of aquatics, 2,000,000 kinds of trees and plants, 1,100,000 kinds of insects and reptiles, 1,000,000 kinds of birds, 3,000,000 kinds of four-legged beasts, and 400,000 kinds of human species.

Our Most Revered Paramgurudev—Padpadma Nityalīlā Pravista Om 108 Śrī Śrī Bhakti Siddhānta Sarasvatī Thakur Prabhupād had spoken on the above verse.

Once Śrīla Prabhupād was preaching in Calcutta to two students of Scottish Church College. He said that he was not satisfied. Revered Śrīla Paramgurudev said that even a moment of human birth should not be wasted. They have to go back to their homes.

Śrīla Prabhupād said, “tirumām”—immediately you should start the worship of Supreme Lord.

The two students then said, “Oh! Our house is burning.” Śrīla Prabhupād, “Let it burn.”
The students, “Our neighboring houses will get burnt.”

Śrīla Prabhupād, “Let the entire world burn. You are brahma-bhūta (of the Lord and from the Lord), not saṁsāra-bhūta (of this world and from this world).”

Later the two students stayed in the Math.

The human birth is very rare. One should not lose this precious opportunity. Other living entities have no capacity to worship the Supreme Lord. Only human beings have the capacity to worship. So it is not wise to lose this precious human birth because intense austerities for eternal welfare is not possible in other births.

Immediately start bhajan

In Śrīmad Bhāgavatam (11.9.29) it is said,

labdhvā su-durlabham idam bahu-sambhavānte
mānuṣyam artha-dam anityam apīha dhīrah
tūrṇaṁ yateta na pated anumṛtyu yāvan
niḥśreyasāya viṣayaḥ khalu sarvataḥ syāt

“After innumerable births, we have been born as human beings. Therefore, this human birth, though very rare, although impermanent, it bestows the highest benefit. Hence the duty of human beings is to try to achieve the highest welfare. Therefore a person, who has got the actual knowledge will endeavor for highest eternal welfare. Because intense suffering can be achieved from mundane pleasure objects, but the actual welfare is possible only through devotion to the Supreme Lord.”

Śrī Prahlād Mahārāj instructs in Śrīmad Bhāgavatam (7.6.1)

kaumāra ācaret prājño dharmān bhāgavatān iha
durlabham mānuṣam janma tad apy adhruvam arthadam

‘One who is sufficiently intelligent should use the human form of body from the tender age of childhood to practice the activities of devotional service, giving up all other engagements. The human body is most rarely achieved, and although temporary like other bodies, it is meaningful because in human life one can perform devotional service.’

Hence it is unwise to use this human birth, which is rare, for transitory happiness. We may lose this opportunity any time. We will fall down to lower species.

Pastime of King Bharat

It happened with king Bharat. He left his kingdom and family to worship Supreme Lord. In the forest when he went to fetch some water, he saw a pregnant female deer jumping over the water stream. She gave birth to a child-deer and died. Thinking that the child is motherless, he started taking care of him and in the process he got attached to the child- deer. Since he remembered the deer at the time of his death, he had to take birth as a deer in his next life. But he remembered his past life and also the reason for his birth as a deer. He did not mix with other deers, instead associated with sadhus. In his subsequent next life he became Jada Bharat and attained Lord.