The second cause whence these rebellions sometimes proceed is the devil, who, in order to disquiet and disturb the soul, at times when it is at prayer or is striving to pray, contrives to stir up these motions of impurity in its nature; and if the soul gives heed to any of these, they cause it great harm. For through fear of these not only do persons become lax in prayer—which is the aim of the devil when he begins to strive with them—but some give up prayer altogether, because they think that these things attack them more during that exercise than apart from it, which is true, since the devil attacks them then more than at other times, so that they may give up spiritual exercises.
The flesh resists this daily humiliation, first by a frontal attack, and later by hiding itself under the words of the spirit (i.e. in the name of 'evangelical liberty'). We claim liberty from all legal compulsion, from self-martyrdom and mortification, and play this off against the proper evangelical use of discipline and asceticism; we thus excuse our self-indulgence and irregularity in prayer, in meditation and in our bodily life. But the contrast between our behavior and the word of Jesus is all too painfully evident. We forget that discipleship means estrangement from the world, and we forget the real joy and freedom which are the outcome of a devout rule of life. As soon as a Christian recognizes that he has failed in his service, that his readiness has become feeble, and that he has sinned against another's life and become guilty of another's guilt, that all his joy in God has vanished and that his capacity for prayer has quite gone, it is high time for him to launch an assault upon the flesh, and prepare for better service by fasting and prayer (Luke 2:37; 4:2: Mark 9:29; 1 Cor. 7:5).