Spiritual life means voluntarily accepting some austerities for the sake of God realization. That is why we insist on no illicit sex, meat-eating, gambling, or intoxication for our initiated students. Without these restrictions, any "yoga meditation" or so-called spiritual discipline cannot be genuine. It is simply a business deal between the cheaters and the cheated.
(Srila Prabhupada, in SSR, Separating the Saints from the Swindlers)