Everyone is trying to be happy, and the process adopted to achieve that happiness is called self-interest. Unfortunately, the conditioned soul hovering within this material world does not know that his ultimate goal of self-interest is Vāsudeva. Saṁsṛti, or material existence, begins with the illusioned bodily conception of life, and on the basis of this conception there ensues a series of unwanted things (anarthas). These unwanted things are actually mental desires for various types of sense gratification. In this way one accepts different types of bodies within this material world. One first has to control the mind so that the desires of the mind can be purified. This process is described in the Nārada-pañcarātra as sarvopādhi-vinirmuktaṁ tatparatvena nirmalam (CC.2:19:170). Unless one purifies his mind, there is no question of getting free from the material condition.
(Srimad Bhagavatam----4:29:36-37----purport).

A living entity too much absorbed in material activity becomes very much attracted to the material body. Even at the point of death, he thinks of his present body and the relatives connected to it. Thus he remains fully absorbed in the bodily conception of life, so much so that even at the point of death he abhors leaving his present body. Sometimes it is found that a person on the verge of death remains in a coma for many days before giving up the body. This is common among so-called leaders and politicians who think that without their presence the entire country and all society will be in chaos. This is called māyā. Political leaders do not like to leave their political posts, and they either have to be shot by an enemy or obliged to leave by the arrival of death. By superior arrangement a living entity is offered another body, but because of his attraction to the present body, he does not like to transfer himself to another body. Thus he is forced to accept another body by the laws of nature.
(Srimad Bhagavatam----4:29:76-77----purport).

This material creation is the spirit soul's dream. Actually all existence in the material world is a dream of Mahā-Viṣṇu, as the Brahma-saṁhitā describes:
yaḥ kāraṇārṇava-jale bhajati sma yoga-
nidrām ananta-jagad-aṇḍa-saroma-kūpaḥ
(Bs. 5.47)
This material world is created by the dreaming of Mahā-Viṣṇu. The real, factual platform is the spiritual world, but when the spirit soul wants to imitate the Supreme Personality of Godhead, he is put into this dreamland of material creation. After being in contact with the material modes of nature, the living entity develops the subtle and gross bodies. When the living entity is fortunate enough to associate with Śrī Nārada Mahāmuni or his servants, he is liberated from this dreamland of material creation and the bodily conception of life.
(Srimad Bhagavatam----4:29:83----purport).

As soon as someone thinks, "I am this material body (ahaṁ mameti (S.B.5:5:8) and everything in relationship with this material body is mine," he is in illusion (moha). This illusion caused by the material energy acts especially on the conditioned souls, but it sometimes also acts on liberated souls as well. A liberated soul is a person who has sufficient knowledge of this material world and is therefore unattached to the bodily conception of life. But because of association with the modes of material nature for a very long time, even liberated souls sometimes become captivated by the illusory energy due to inattentiveness in the transcendental position. Therefore Lord Kṛṣṇa says in Bhagavad-gītā (7.14), mām eva ye prapadyante māyām etāṁ taranti te: "Only those who surrender unto Me can overcome the influence of the material energy." Therefore no one should think of himself as a liberated person immune to the influence of māyā. Everyone should very cautiously execute devotional service by rigidly following regulative principles. Thus he will remain fixed at the lotus feet of the Lord.
(Srimad Bhagavatam----5:18:4----purport).

The misunderstanding of the conditioned soul is the bodily conception of life. The body is material, but within the body is the soul. This is spiritual understanding. Unfortunately, one who is in ignorance, under the spell of material illusion, accepts the body to be the self. He cannot understand that the body is matter. Like small particles of sand, bodies come together and are separated by the force of time, and people falsely lament for unification and separation. Unless one knows this, there is no question of happiness.
(Srimad Bhagavatam----6:15:3----purport).

Everyone should be interested in the activities of the spirit soul, not the body. As long as one is activated by the bodily conception of life, there is always the danger of being misled, whether one is a man or a woman. The soul is sometimes described as puruṣa because whether one is dressed as a man or a woman, one is inclined to enjoy this material world. One who has this spirit of enjoyment is described as puruṣa. Whether one is a man or a woman, he is not interested in serving others; everyone is interested in satisfying his or her own senses. Kṛṣṇa consciousness, however, provides first-class training for a man or a woman. A man should be trained to be a first-class devotee of Lord Kṛṣṇa, and a woman should be trained to be a very chaste follower of her husband. That will make the lives of both of them happy.
(Srimad Bhagavatam----6:18:42----purport).

A material body is manufactured by the external energy according to the direction of the Supreme Personality of Godhead. The conditioned soul, being seated on this machine, wanders throughout the universe, and because of his bodily conception of life he only suffers. Actually the suffering of being blasphemed and the enjoyment of being praised, the acceptance of a good welcome or of chastisement by harsh words, are felt in the material conception of life; but since the body of the Supreme Personality of Godhead is not material but sac-cid-ānanda-vigraha (Bs. 5.1), He is unaffected by insults or greetings, blasphemy or prayers. Being always unaffected and complete, He does not feel extra pleasure when offered nice prayers by the devotee, although the devotee benefits by offering prayers to the Lord. Indeed, the Lord is very kind to His so-called enemy because one who always thinks of the Personality of Godhead as an enemy also benefits, although he thinks of the Lord adversely. If a conditioned soul, thinking of the Lord as an enemy or a friend, somehow or other becomes attached to the Lord, he receives great benefit.
(Srimad Bhagavatam----7:1:23----purport).

Because of being covered by material bodies, the conditioned souls, including even greatly learned scholars and falsely educated professors, all think that as soon as the body is finished, everything is finished. This is due to their bodily conception of life. Kṛṣṇa has no such bodily conception, nor is His body different from His self. Therefore, since Kṛṣṇa has no material conception of life, how can He be affected by material prayers and accusations? Kṛṣṇa's body is described herewith as kaivalya, nondifferent from Himself. Since everyone has a material bodily conception of life, if Kṛṣṇa had such a conception what would be the difference between Kṛṣṇa and the conditioned soul? Kṛṣṇa's instructions in Bhagavad-gītā are accepted as final because He does not possess a material body. As soon as one has a material body he has four deficiencies, but since Kṛṣṇa does not possess a material body, He has no deficiencies. He is always spiritually conscious and blissful. Īśvaraḥ paramaḥ kṛṣṇaḥ sac-cid-ānanda-vigrahaḥ (Bs. 5.1): His form is eternal, blissful knowledge. Sac-cid-ānanda-vigrahaḥ, ānanda-cinmaya-rasa and kaivalya are the same.
(Srimad Bhagavatam----7:1:25----purport).

We see materialistic persons busily engaged in economic development all day and all night, trying to increase their material opulence, but even if we suppose that they get some benefit from such endeavors, that does not solve the real problem of their lives. Nor do they know what the real problem of life is. This is due to a lack of spiritual education. Especially in the present age, every man is in darkness, in the bodily conception of life, not knowing anything of the spirit soul and its needs. Misguided by the blind leaders of society, people consider the body to be everything, and they are engaged in trying to keep the body materially comfortable. Such a civilization is condemned because it does not lead humanity toward knowing the real goal of life. People are simply wasting time and the valuable gift of the human form because a human being who does not cultivate spiritual life but dies like the cats and dogs is degraded in his next life. From human life, such a person is put into the cycle of continuous birth and death. Thus one loses the true benefit of human life, which is to become Kṛṣṇa conscious and solve life's problems.
(Srimad Bhagavatam----7:5:6:4----purport).

The spirit soul (ātmā or jīva) is certainly different from the body, which is a combination of five material elements. This is a simple fact, but it is not understood unless one is spiritually educated. Kaśyapa Muni met his wife, Aditi, in the heavenly planets, but the same misconception extends throughout the entire universe and is also here on earth. There are different grades of living entities, but all of them are more or less under the impression of the bodily conception of life. In other words, all living entities in this material world are more or less devoid of spiritual education. The Vedic civilization, however, is based on spiritual education, and spiritual education is the special basis on which Bhagavad-gītā was spoken to Arjuna. In the beginning of Bhagavad-gītā, Kṛṣṇa instructed Arjuna to understand that the spirit soul is different from the body.
(Srimad Bhagavatam----8:16:19----purport).

The Gopāla-tāpanī Upaniṣad says that the word bhakti means engagement in the devotional service of the Supreme Personality of Godhead, not of anyone else. This Upaniṣad describes that bhakti is the offering of devotional service unto the Supreme Personality of Godhead. To perform devotional service, one should be relieved of the bodily conception of life and aspirations to be happy through elevation to the higher planetary systems. In other words, work performed simply for the satisfaction of the Supreme Lord, without any desire for material benefits, is called bhakti. Bhakti is also called niṣkarma, or freedom from the results of fruitive activity. Bhakti and niṣkarma are on the same platform, although devotional service and fruitive activity appear almost the same.
(Srimad Bhagavatam----7:5:23-24----purport).