Only when the mind is free from designations can one desire the association of the Supreme Personality of Godhead. The mind must have some occupation. If a person is to be free of material things, his mind cannot be vacant; there must be subject matters for thinking, feeling and willing. Unless one's mind is filled with thoughts of Kṛṣṇa, feelings for Kṛṣṇa and a desire to serve Kṛṣṇa, the mind will be filled with material activities. Those who have given up all material activities and have ceased thinking of them should always retain the ambition to think of Kṛṣṇa. Without Kṛṣṇa, one cannot live, just as a person cannot live without some enjoyment for his mind.
(Sri Caitanya Caritamrta---2:13:138---purport).

When the individual jīva souls are under the control of the internal energy, their only engagement is the satisfaction of Kṛṣṇa, or Viṣṇu. This is the position of a mahātmā. If one is not a mahātmā, he is a durātmā, or a cripple-minded person. Such mentally crippled durātmās are put under the control of the Lord's external potency, mahāmāyā.
(Nectar of instruction).

As stated by Lord Caitanya Mahāprabhu in His Śikṣāṣṭaka instructions, by the chanting of the holy name of the Lord—Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare—or by the process of hearing and chanting of the glories of the Lord, one's mind is gradually cleansed of all dirt. Due to our material association since time immemorial, we have accumulated heaps of dirty things in our minds. The total effect of this takes place when a living entity identifies himself with his body and is thus entrapped by the stringent laws of material nature and put into the cycle of repeated birth and death under the false impression of bodily identification. When one is strengthened by practicing bhakti-yoga, his mind is cleansed of this misunderstanding, and he is no longer interested in material existence or in sense gratification.
(Srimad Bhagavatam---4:21:32---purport).

The Bhagavad-gītā confirms that one will attain his next material body according to his desires at the time he leaves his body. The desire of the mind carries the soul to a suitable atmosphere as the wind carries aromas from one place to another. Unfortunately, those who are not yogīs but gross materialists, who throughout their lives indulge in sense gratification, are puzzled by the disarrangement of the bodily and mental condition at the time of death. Such gross sensualists, encumbered by the main ideas, desires and associations of the lives they have led, desire something against their interest and thus foolishly take on new bodies that perpetuate their material miseries.
(Sri Caitanya Caritamrta---1:5:22---purport).

The people of the world in this age of Kali are always full of anxieties. Everyone is diseased with some kind of ailment. From the very faces of the people of this age, one can find out the index of the mind. Everyone feels the absence of his relative who is away from home. The particular symptom of the age of Kali is that no family is now blessed to live together. To earn a livelihood, the father lives at a place far away from the son, or the wife lives far away from the husband and so on. There are sufferings from internal diseases, separation from those near and dear, and anxieties for maintaining the status quo. These are but some important factors which make the people of this age always unhappy.
(Srimad Bhagavatam---1:16:19---purport).

At the time of death, our state of consciousness determines our next birth. Death destroys the body made up of the five gross elements, but the subtle body, consisting of mind, intelligence, and false ego, remains. As the air carries the scent of the place it blows over, so the soul carries a person's subtle body of mind, intelligence, and false ego, along with his state of consciousness, on to his next birth, and his body is determined accordingly. When a breeze blows over a garden, it carries the fragrance of flowers with it, but when it blows over a rubbish heap, the breeze is filled with the stench. Similarly, the activities a person performs during his lifetime continuously influence his mentality, and at the time of death the cumulative effect of these activities determines his state of consciousness. Thus the subtle body formed during one's lifetime is carried over to one's next birth and manifests as the soul's next gross body. Naturally, therefore, the gross body reflects one's state of consciousness. As the popular saying goes, "The face is the index of the mind." And the mind is the product of the activities of one's present and previous lives. In other words, one's mind, intelligence, and false ego, which are influenced by one's habits in this and previous births, form the matrix that determines the type of body and mentality one will have in the next life. Hence the connection between one's previous, present, and future lives is the mind, intelligence, and false ego.
(Renunciation Through Wisdom).