It is already explained that one may externally control the senses by some artificial process, but unless the senses are engaged in the transcendental service of the Lord, there is every chance of a fall. Although the person in full Kṛṣṇa consciousness may apparently be on the sensual plane, because of his being Kṛṣṇa conscious he has no attachment to sensual activities. The Kṛṣṇa conscious person is concerned only with the satisfaction of Kṛṣṇa, and nothing else. Therefore he is transcendental to all attachment and detachment. If Kṛṣṇa wants, the devotee can do anything which is ordinarily undesirable; and if Kṛṣṇa does not want, he shall not do that which he would have ordinarily done for his own satisfaction. Therefore to act or not to act is within his control because he acts only under the direction of Kṛṣṇa. This consciousness is the causeless mercy of the Lord, which the devotee can achieve in spite of his being attached to the sensual platform.
(Bhagavad-Gita-------2:64-------purport).

Of the saintly persons who are constantly engaged in striving toward salvation, one who is in Kṛṣṇa consciousness is the best of all. The Bhāgavatam (4.22.39) confirms this fact as follows:
yat-pāda-paṅkaja-palāśa-vilāsa-bhaktyā
karmāśayaṁ grathitam udgrathayanti santaḥ
tadvan na rikta-matayo yatayo 'pi ruddha-
sroto-gaṇās tam araṇaṁ bhaja vāsudevam
"Just try to worship, in devotional service, Vāsudeva, the Supreme Personality of Godhead. Even great sages are not able to control the forces of the senses as effectively as those who are engaged in transcendental bliss by serving the lotus feet of the Lord, uprooting the deep-grown desire for fruitive activities."

In the conditioned soul the desire to enjoy the fruitive results of work is so deep rooted that it is very difficult even for the great sages to control such desires, despite great endeavors. A devotee of the Lord, constantly engaged in devotional service in Kṛṣṇa consciousness, perfect in self-realization, very quickly attains liberation in the Supreme. Owing to his complete knowledge in self-realization, he always remains in trance.

(Bhagavad-Gita-------5:26-------purport).

Because of the appearance of the autumn season, the water of the ocean becomes calm and quiet, just as a person developed in self-realization becomes free from disturbance by the three modes of material nature. In autumn, farmers save the water within the fields by building strong walls so that the water contained within the field cannot run out. There is hardly any hope for new rainfall; therefore they want to save whatever is in the field. Similarly, a person who is actually advanced in self-realization protects his energy by controlling the senses. It is advised that after the age of fifty one should retire from family life and conserve the energy of the body for utilization in the advancement of Kṛṣṇa consciousness. Unless one is able to control the senses and engage them in the transcendental loving service of Mukunda, there is no possibility of salvation.

(Krsna Book).

If one wants to make steady progress on the path of self-realization, he must try to control the forces of the material senses. There are the forces of talk, forces of anger, forces of mind, forces of the stomach, forces of the genitals, and forces of the tongue. One who is able to control the forces of all these different senses, and the mind, is called gosvāmī, or svāmī. Such gosvāmīs live strictly controlled lives, and forgo altogether the forces of the senses. Material desires, when unsatiated, generate anger, and thus the mind, eyes and chest become agitated. Therefore, one must practice to control them before one gives up this material body. One who can do this is understood to be self-realized and is thus happy in the state of self-realization. It is the duty of the transcendentalist to try strenuously to control desire and anger.
(Bhagavad-Gita-------5:23-------purport).

The conditioned soul under the clutches of māyā, the material energy, is very much agitated by the urges of the tongue and the genitals. Control of the urges of the tongue, the belly and the genitals (which are situated in a straight line) is called dhṛti. Śrīla Bhaktivinoda Ṭhākura says, tāra madhye jihvā ati, lobhamaya sudurmati. Among the senses, the tongue is the most formidable enemy of the conditioned soul. Urged by the tongue, one commits many sinful activities. Although Kṛṣṇa has given human beings nice food, people still commit sins by killing poor animals for the satisfaction of the tongue. Not being able to control the tongue, the conditioned soul eats more than he needs. Of course, everyone must eat to keep the body fit for the Lord's service, but when one cannot control the senses, he falls victim to the dictations of the tongue and the belly. Naturally, genital agitation follows, and one seeks illicit sex. However, if one is fixed at the lotus feet of Kṛṣṇa, he can control the tongue. Bhaktivinoda Ṭhākura further states, kṛṣṇa baḍa dayāmaya, karibāre jihvā jaya, sva-prasāda-anna dilā bhāi: in order to conquer the tongue, Kṛṣṇa has been very merciful and has given us nice food that has been offered to Him. When a person is attached to Kṛṣṇa's lotus feet, he does not eat anything not offered to Kṛṣṇa. Sei annāmṛta khāo, rādhā-kṛṣṇa-guṇa gāo, preme ḍāka caitanya-nitāi. Since a devotee eats only prasādam, he conquers the dictations of the tongue, belly and genitals. One can control the dictates of the senses when situated in the position of śānta-rasa. Then one's advancement in Kṛṣṇa consciousness is assured.
(Sri Caitanya Caritamrta------2:19:213--------purport).