Text 421
Karma-voga
२०९
PURPORT
The Lord advised Arjuna to regulate the senses from the very beginning so that he could curb the greatest sinful enemy, lust, which destroys the urge for self-realization, and specifically, knowledge of the self.  Jñānam  refers to knowledge of self as distinguished from non-self, or, in other words, knowledge that the spirit soul is not the body.  Vijñānam  refers to specific knowledge of the spirit soul and knowledge of one's constitutional position and his relationship to the Supreme Soul. It is explained thus in the  Śrīmad-Bhāgavatam :  jñānam parama-guhyam me yad-vijñāna-samanvitam/sarahasyam tad-aṅgam ca gṛhāna gaditam mayā : “The knowledge of the self and the Supreme Self is very confidential and mysterious, being veiled by  māyā , but such knowledge and specific realization can be understood if it is explained by the Lord Himself.”  Bhagavad-gītā  gives us that knowledge, specifically knowledge of the self. The living entities are parts and parcels of the Lord, and therefore they are simply meant to serve the Lord. This consciousness is called  Kṛṣṇa  consciousness. So, from the very beginning of life one has to learn this  Kṛṣṇa  consciousness, and thereby one may become fully  Kṛṣṇa  conscious and act accordingly.
Lust is only the perverted reflection of the love of God which is natural for every living entity. But if one is educated in Krṣṇa consciousness from the very beginning, that natural love of God cannot deteriorate into lust. When love of God deteriorates into lust, it is very difficult to return to the normal condition. Nonetheless, Krṣṇa consciousness is so powerful that even a late beginner can become a lover of God by following the regulative principles of devotional service. So, from any stage of life, or from the time of understanding its urgency, one can begin regulating the senses in Krṣṇa consciousness, devotional service of the Lord, and turn the lust into love of Godhead—the highest perfectional stage of human life.
TEXT 42
इन्द्रियाणि पराण्याहुरिन्द्रियेभ्यः परं मनः । मनसस्तु परा बुद्धियों बुद्धेः परतस्तु सः ॥४२॥
indriyāṇi parāṇy āhur  
 indriyebhyaḥ paraṁ manaḥ  
 manasas tu parā buddhir  
 yo buddheḥ paratas tu saḥ