This verse is from Srimad-Bhagavatam (11.19.36). The conditioned soul under the clutches of maya, 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 dhrti. Srila Bhaktivinoda Thakura says, tara madhye jihva 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 Krsna 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 Krsna, he can control the tongue. Bhaktivinoda Thakura further states, krsna bada dayamaya, karibare jihva jaya, sva-prasada-anna dila bhai: in order to conquer the tongue, Krsna has been very merciful and has given us nice food that has been offered to Him. When a person is attached to Krsna's lotus feet, he does not eat anything not offered to Krsna. Sei annamrta khao, radha-krsna-guna gao, preme daka caitanya-nitai. Since a devotee only eats prasada, he conquers the dictations of the tongue, belly and genitals. One can control the dictates of the senses when situated in the position of santa-rasa. Then one's advancement in Krsna consciousness is assured.