One who can approach that spiritual sky is not required to descend again to the material sky. In the material sky, even if we approach the highest planet (Brahmaloka), what to speak of the moon, we will find the same conditions of life, namelybirth, death, disease and old age. No planet in the material universe is free from these four principles of material existence.
(Bhagavad-Gita---introduction).

Yet Bhagavad-gītā does not advise us to go to any of the planets in this material world, because even if we go to Brahmaloka, the highest planet, through some sort of mechanical contrivance by maybe traveling for forty thousand years (and who would live that long?), we will still find the material inconveniences of birth, death, disease and old age. But one who wants to approach the supreme planet, Kṛṣṇaloka, or any of the other planets within the spiritual sky, will not meet with these material inconveniences.
(Bhagavad-Gita---introduction).

Birth, death, old age and diseases affect this material body, but not the spiritual body. There is no birth, death, old age and disease for the spiritual body, so one who attains a spiritual body, becomes one of the associates of the Supreme Personality of Godhead and engages in eternal devotional service is really liberated. Ahaṁ brahmāsmi: I am spirit. It is said that one should understand that he is Brahman, spirit soul. This Brahman conception of life is also in devotional service, as described in this verse. The pure devotees are transcendentally situated on the Brahman platform, and they know everything about transcendental activities.
(Bhagavad-Gita----7:29----purport).

Humility; pridelessness; nonviolence; tolerance; simplicity; approaching a bona fide spiritual master; cleanliness; steadiness; self-control; renunciation of the objects of sense gratification; absence of false ego; the perception of the evil of birth, death, old age and disease; detachment; freedom from entanglement with children, wife, home and the rest; even-mindedness amid pleasant and unpleasant events; constant and unalloyed devotion to Me; aspiring to live in a solitary place; detachment from the general mass of people; accepting the importance of self-realization; and philosophical search for the Absolute Truth—all these I declare to be knowledge, and besides this whatever there may be is ignorance.
(Bhagavad-Gita----13:8-12----translation).

One should try to understand the distress of accepting birth, death, old age and disease. There are descriptions in various Vedic literatures of birth. In the Śrīmad-Bhāgavatam the world of the unborn, the child's stay in the womb of the mother, its suffering, etc., are all very graphically described. It should be thoroughly understood that birth is distressful. Because we forget how much distress we have suffered within the womb of the mother, we do not make any solution to the repetition of birth and death.
(Bhagavad-Gita----13:8-12----purport).

No one wants to be diseased, and no one wants to become old, but there is no avoiding these. Unless we have a pessimistic view of this material life, considering the distresses of birth, death, old age and disease, there is no impetus for our making advancement in spiritual life.
(Bhagavad-Gita----13:8-12----purport).

The prison house of the material world is created by Brahmā under instruction of the Personality of Godhead, and at the conclusion of a kalpa the whole thing is destroyed by Śiva. But as far as maintenance of the prison house is concerned, it is done by Viṣṇu, as much as the state prison house is maintained by the state. Anyone, therefore, who wishes to get out of this prison house of material existence, which is full of miseries like repetition of birth, death, disease and old age, must please Lord Viṣṇu for such liberation.
(Srimad Bhagavatam----1:2:23----purport).

The miseries and mixed happiness of all living beings are only of different degree and quality, but no one is free from the miseries of birth, death, old age and disease. Similarly, everyone has his destined happiness also. No one can get more or less of these things simply by personal endeavors. Even if they are obtained, they can be lost again. One should not, therefore, waste time with these flimsy things; one should only endeavor to go back to Godhead. That should be the mission of everyone's life.
(Srimad Bhagavatam----1:5:18----purport).

This clearance of the misgivings of material existence at once takes place by association with the Lord's devotees, who are able to inject the transcendental sound into the depths of the bewildered heart and thus make one practically liberated from all lamentation and illusion. That is a summary of the pacifying measures for those affected by the reaction of stringent material laws, exhibited in the forms of birth, death, old age and disease, which are insoluble factors of material existence. The victims of war, namely, the family members of the Kurus, were lamenting the problems of death, and the Lord pacified them on the basis of knowledge.
(Srimad Bhagavatam----1:8:4----purport).

The time limitation even of the sun is of no concern, and so what to speak of the Supreme Lord who is the creator and controller of the sun. Therefore, in the Bhagavad-gītā it is stated that anyone who factually understands the transcendental appearance and disappearance of the Lord by His inconceivable energy becomes liberated from the laws of birth and death and is placed in the eternal spiritual sky where the Vaikuṇṭha planets are. There such liberated persons can eternally live without the pangs of birth, death, old age and disease. In the spiritual sky the Lord and those who are eternally engaged in the transcendental loving service of the Lord are all eternally young because there is no old age and disease and there is no death.
(Srimad Bhagavatam----1:15:32----purport).

Foolish, faithless creatures try to avoid the existence of the Lord and proclaim themselves secular at the cost of valuable human life. The human life is especially meant for knowing the science of God, but foolish creatures, especially in this age of Kali, instead of knowing God scientifically, make propaganda against religious belief as well as the existence of God, even though they are always bound by the laws of God by the symptoms of birth, death, old age and disease.
(Srimad Bhagavatam----1:17:10-11----purport).

The systematic hearing of the transcendental activities, qualities and names of Lord Śrī Kṛṣṇa pushes one towards eternal life. Systematic hearing means knowing Him gradually in truth and fact, and this knowing Him in truth and fact means attaining eternal life, as stated in the Bhagavad-gītā. Such transcendental, glorified activities of Lord Śrī Kṛṣṇa are the prescribed remedy for counteracting the process of birth, death, old age and disease, which are considered to be material awards for the conditioned living being. The culmination of such a perfectional stage of life is the goal of human life and the attainment of transcendental bliss.
(Srimad Bhagavatam----1:18:10----purport).