The following comes from John of the Cross taken his book, Dark Night of the Soul. This is a continuation of his discussion of the "seven capital sins" of the spiritual life. In previous posts, he has discussed spiritual pride, spiritual greed, spiritual luxury, and spiritual wrath. In this post, he will warn against spiritual gluttony.
The fifth sin is spiritual gluttony. Many souls become addicted to the spiritual sweetness of the devotional life and strive to obtain more and more of it. They pass beyond the limits of moderation and nearly kill themselves with spiritual exercises.
They will often try to subdue their flesh with great acts of submission, lengthy fasts and painful penances. But note: these are one sided penances; they do not come from God. Such persons are working their own will, and thus grow in vice rather than in virtue.
They are not walking in true obedience, but rather, are doing what they want in the time and measure what they have chosen. They do these things not for God but for themselves, and for this reason they will soon grow weary in them. For this reason, it is probably better for these persons to give up their devotions entirely.
The problem is this: when they have received no pleasure for their devotions, they think they have not accomplished anything. This is a grave error, and it judges God unfairly. For the truth is that the feelings we receive from our devotional life are the least of its benefits. The invisible and unfelt grace of God is much greater, and it is beyond our comprehension.
(Cited in Richard Foster’s, Devotional Classics, pp. 34-35)