Modern civilization is based on this defective idea that, "I am this body." "I am Indian," "I am American," "I am Hindu," "I am Muslim," "I am Christian"—these are all bodily concept of life. "Because I have got this body from a Christian father and mother, therefore I am a Christian." But I am not this body, "Because I have got this body from a Hindu father and mother, therefore I am Hindu." But I am not this body. So for spiritual understanding, this is the basic principle to understand that, "I am not this body; I am soul," ahaṁ brahmāsmi. This is the Vedic instruction: "Try to understand that you are spirit soul; you are not this body."
The yoga system is practiced just to understand this. Yoga indriya saṁyamaḥ. By controlling the senses, especially the mind . . . mind is the master or the chief of the senses. Manaḥ-ṣaṣṭhānīndriyāṇi prakṛti-sthāni karṣati (BG 15.7). We are undergoing a struggle for existence with this mind and the senses under the false conception of identifying this body as self. So if we concentrate our mind by controlling the senses, then we can gradually understand. Dhyānāvasthita-tad-gatena manasā paśyanti yaṁ yoginaḥ (SB 12.13.1). The yogīs, they meditate upon the Supreme Person, Viṣṇu, and by that process they realize the self. Self-realization is the prime object of human life. So the beginning of self-realization is to understand that "I am not this body; I am spirit soul." Ahaṁ brahmāsmi.
So these things are very nicely explained in the Bhagavad-gītā. If we simply read Bhagavad-gītā carefully, under proper guidance, then everything will be clear, without any difficulty, that "I am not this body; I am spirit soul. My business is different than this bodily concept of life. I shall never be happy taking . . . accepting this body as self. That is a wrong foundation of knowledge." In this way, if we make progress, then we shall understand, ahaṁ brahmāsmi: "I am spirit soul." Then "Wherefrom I have come?" Everything is described in the Bhagavad-gītā, that the spirit soul, Kṛṣṇa says, the Lord says, mamaivāṁśo jīva-bhūtaḥ (BG 15.7): "These living entities, they are My part and parcel, fragment, or minute sparks." As the big fire and the small fire, both of them are fire, but big fire and small fire. So far the fire quality is concerned, God and we are the same.