The road and ascent to God, then, necessarily demands a habitual effort to renounce and mortify the appetites; the sooner this mortification is achieved, the sooner the soul reaches the top. But until the appetites are eliminated, a person will not arrive, no matter how much virtue he practices. For he will fail to acquire perfect virtue, which lies in keeping the soul empty, naked, and purified of every appetite. ... Until slumber comes to the appetites through the mortification of sensuality, and until this very sensuality is stilled in such a way that the appetites do not war against the spirit, the soul will not walk out to genuine freedom, to the enjoyment of union with its Beloved.

(Saint John of the Cross)