One who, however, follows the rules and regulations of married life, having a sexual relationship only with his wife (and that also under regulation), is also called a brahmacari. Such a restrained householder brahmacari may be accepted in the bhakti school, but the jnana and dhyana schools do not even admit householder brahmacaris. They require complete abstinence without compromise. In the bhakti school, a householder brahmacari is allowed controlled sex life because the cult of bhakti-yoga is so powerful that one automatically loses sexual attraction, being engaged in the superior service of the Lord. In the Bhagavad-gita (2.59) it is said:
visaya vinivartante
niraharasya dehinah
rasa-varjam raso ‘py asya
param drstva nivartate
Whereas others are forced to restrain themselves from sense gratification, a devotee of the Lord automatically refrains because of superior taste. Other than the devotee, no one has any information of that superior taste.
Srila Prabhupada Bg 6.13-14, purport