One should be satisfied with whatever means of life comes automatically. The modern materialistic civilization is just the opposite of the ideal civilization. Every day the so-called leaders of modern society invent something contributing to a cumbersome way of life that implicates people more and more in the cycle of birth, death, old age and disease.
(Srimad Bhagavatam----7:14:5----purport).

For a bewildered person in the materialistic way of life, the body, the mind and the senses, which are engaged in sense gratification, are the cause of bondage to repeated birth, death, old age and disease. But for one who is advanced in spiritual knowledge, the same body, senses and mind are the cause of liberation.
(Srimad Bhagavatam----7:15:41----purport).

The Lord exists at all times. This is extremely difficult for a nondevotee to understand. Although the transcendental Supreme Personality of Godhead is perceivable by everyone, only the pure devotees perceive His presence and activities. The Supreme Personality of Godhead is completely free from material birth, death, old age and disease.
(Srimad Bhagavatam----8:3---summary).

The material body, whether in the higher or lower planetary system, is destined to die. In the lower planetary system or lower species of life one may die soon, and in the higher planets or higher species one may live for a long, long time, but death is inevitable. This fact should be understood. In the human form of life one should take the opportunity to put an end to birth, death, old age and disease by performing tapasya.
(Srimad Bhagavatam----9:13:10----purport).

The living entities come to this material world in the spirit of enjoyment, but because they want to enjoy without Kṛṣṇa (kṛṣṇa-bahirmukha haiyā bhoja-vāñchā kare), they suffer birth, death, old age and disease under the control of the illusory energy. When the Supreme Personality of Godhead appears, however, no such causes are involved; His descent is an act of His pleasure potency. We should always remember this distinction between the Lord and the ordinary living entity and not uselessly argue that the Lord cannot come.
(Srimad Bhagavatam----10:2:39----purport).

Since Kṛṣṇa is not subject to birth, death, old age or disease, and since we are part and parcel of Kṛṣṇa, we also are not subject to birth, death, old age and disease, but we have become subject to these illusory problems because of our forgetfulness of Kṛṣṇa and our position as His eternal servants (jīvera 'svarūpa' haya-kṛṣṇera 'nitya-dāsa'.
(Srimad Bhagavatam----10:2:39----purport).

As stated in Bhagavad-gītā (13.9), janma-mṛtyu jarā-vyādhi-duḥkha-doṣānudarśanam: birth, death, old age and disease are certainly the primary distresses of the material world. People are trying to control birth, but they are not able to control death; and if one cannot control death, one cannot control birth either. In other words, artificially controlling birth is not any more feasible than artificially controlling death.
(Srimad Bhagavatam----10:3:33----purport).

"A person acting in the service of Kṛṣṇa with his body, mind and words is a liberated person, even within the material world." (Bhakti-rasāmṛta-sindhu 1.2.187) Therefore, one is forbidden to regard the guru as an ordinary human being (guruṣu nara-matir. .. nārakī saḥ). The spiritual master, or ācārya, is always situated in the spiritual status of life.Birth, death, old age and disease do not affect him. According to the Hari-bhakti-vilāsa, therefore, after the disappearance of an ācārya, his body is never burnt to ashes, for it is a spiritual body. The spiritual body is always unaffected by material conditions.
(Srimad Bhagavatam----10:4:20----purport).

When the modes of passion and ignorance increase in human society, giving rise to unnecessary economic development, the result is that people become involved with wine, women and gambling. Then, being mad, they maintain big slaughterhouses or occasionally go on pleasure excursions to kill animals. Forgetting that however one may try to maintain the body, the body is subject to birth, death, old age and disease, such foolish rascals engage in sinful activities, one after another. Being duṣkṛtīs, they completely forget the existence of the supreme controller, who is sitting within the core of everyone's heart (īśvaraḥ sarva-bhūtānāṁ hṛd-deśe 'rjuna tiṣṭhati.
(Srimad Bhagavatam----10:10:9----purport).

By pious fruitive work one is placed in a position where he can temporarily feel material happiness, whereas vicious activities lead him to a distressful position of material want and scarcity. However, even if one is put into the most perfect situation of material happiness, he cannot in that way become free from the pangs of birth, death, old age and disease. A materially happy person is therefore in need of the eternal relief that mundane religiosity in terms of fruitive work can never award.
(Sri Caitanya Caritamrta----1:1:91----purport).

Mystic powers can make a yogī materially powerful and thus give temporary relief from the miseries of birth, death, old age and disease, as other material sciences can also do, but such mystic powers can never be a permanent source of relief from these miseries. Therefore, according to the Bhāgavata school, this path of religiosity is also a method of cheating its followers. In the Bhagavad-gītā it is clearly defined that the most elevated and powerful mystic yogī is one who can constantly think of the Supreme Lord within his heart and engage in the loving service of the Lord.
(Sri Caitanya Caritamrta----1:1:91----purport).

In the grim clutches of māyā, the first-class prisoners of this material world wrongly think themselves happy because they are rich, powerful, resourceful and so on. These foolish creatures do not know that they are nothing but play dolls in the hands of material nature and that at any moment material nature's pitiless intrigues can crush to dust all their plans for godless activities. Such foolish prisoners cannot see that however they improve their position by artificial means, the calamities of repeated birth, death, disease and old age are always beyond the jurisdiction of their control. Foolish as they are, they neglect these major problems of life and busy themselves with false things that cannot help them solve their real problems.
(Sri Caitanya Caritamrta----1:3:98----purport).

The laws of material nature are so strong that none of our material possessions can save us from the cruel hands of death. In the Bhagavad-gītā (13.9) it is stated, janma-mṛtyu-jarā-vyādhi-duḥkha-doṣānudarśanam: one who is actually advancing must always consider the four principles of miserable life, namely, birth, death, old age and disease. One cannot be saved from all these miseries unless he takes shelter of the lotus feet of the Lord.
(Sri Caitanya Caritamrta----1:7:1----purport).

The Kṛṣṇa consciousness movement introduced by Lord Caitanya is extremely important because one who takes to it becomes eternal, being freed from birth, death and old age. People do not recognize that the real distresses in life are the four principles of birth, death, old age and disease. They are so foolish that they resign themselves to these four miseries, not knowing the transcendental remedy of the Hare Kṛṣṇa mahā-mantra.
(Sri Caitanya Caritamrta----1:9:39----purport).

Every living entity is wandering within the universe, subjected to the law of karma and transmigrating from one body to another and from one planet to another. Therefore the whole Vedic process is meant to save the wandering living entities from the clutches of māyā—birth, death, disease and old age. This means stopping the cycle of birth and death. This cycle can be stopped only if one worships Kṛṣṇa.
(Sri Caitanya Caritamrta----2:3:181----purport).

One's relationship with the Supreme Personality of Godhead may be reestablished even after one has fallen into the ocean of nescience, which is the ocean of material existence involving the repetition of birth, death, old age and disease, all arising out of the acceptance of the material body.
(Sri Caitanya Caritamrta----2:11:151----purport).