"the sensory benefits are the least among those that this Most Blessed Sacrament bestows, for the invisible grace it gives is a greater blessing. God often withdraws sensory delight and pleasure so that souls might set the eyes of faith upon this invisible grace. Not only in receiving communion, but in other spiritual exercises as well, beginners desire to feel God and taste of Him as if He were comprehensible and accessible. This desire is a serious imperfection and, because it involves impurity of faith, opposed to God's way."
St. John of the Cross, The dark night I.6 ("The imperfections of spiritual gluttony").5, trans. Kieran Kavanaugh, O.C.D. and Otilio Rodriguez, O.C.D.; The collected works of St. John of the Cross (Washington, D.C.: ICS Publications, Institute of Carmelite Studies, 1973), 308.