"When your heart feels itself moved by the vain joy in natural goods, remember how futile, perilous, and pernicious it is to rejoice in anything except in the service of God. Consider how great an evil it was for the angels to rejoice and take pleasure in their beauty and natural endowments, since it was this that plunged them into the abyss of sin. Remember, too, how many evils befall men [and women] daily owing to this same vanity, and resolve (while there is still time) to employ the remedy which the poet recommends to those who are becoming attached to these things: Make haste and apply the remedy at the outset; for when evil has had time to grow in the heart it is too late to apply the remedy and the medicine."
"The principal evils into which a person may fall by taking a vain joy in their good works and habits . . . are all very harmful because they are spiritual in nature.
The first evil is vanity, including pride, vainglory, and presumption; for a person cannot rejoice in their works without esteeming them highly; and this leads to boasting and such-like things, as we are told of the Pharisee in the Gospel, who prayed and congratulated himself before God, boasting about his fasting and his other good works (Luke 18:12)
The second evil is usually linked with the first: it consists in judging others as wicked, imperfect, and inferior to us, by comparing their acts and good works with our own. Some go even so far as to become angry and envious when they see others are praised, or do more good works, or are more deserving (of praise) than themselves.
The third kind of evil . . . is in those who, since they look for pleasure in the good works they perform, do them only as they see that some pleasure and praise will result from them. And thus, as Christ says, they do everything 'in order to be seen by men' and not for the love of God alone.
The fourth evil . . . : these persons will have no reward from God, since they have desired to find in this life joy or consolation or honor or the satisfaction of some other kind of selfish interest in the performance of their good works. Of these our Saviour says that they have already received their reward . . . . Are we not justified in saying of some people that in the good works they perform they are worshiping themselves more than God? This is the sounding of the trumpet, which, as our Saviour says, is done by vain men. (Matt. 6:3)
The fifth evil . . . is manifest in the fact that such persons make no progress on the road to perfection . . . for, since they are attached to the pleasure and consolation which they find in their good works, it follows that when such pleasure and consolation are absent they slacken and do not persevere.
The sixth evil lies in the fact that such persons commonly deceive themselves, thinking that the thing and good works which give them pleasure are better than those which give them none. And yet, as a rule, those works in which a man practices the greatest self-denial are more acceptable and precious in the sight of God than are those in which he finds consolation and which may very easily become an occasion of self-seeking.
The seventh evil derives from the fact that to the extent that a person does not stifle their vain rejoicing in the performance of morals acts, they are incapable of accepting reasonable counsel and instruction in regard to the works they ought to do. For they are fettered by the habit of weakness which they have acquired in performing good works while they were attached to this vain joy. Such a person is greatly weakened in their love of God and their neighbor; for the self-love which governs them in relation to their good works cause their love of God to grow cold."
excerpts from St. John of the Cross "The Dark Night of the Soul"
"The dark nights which come to the inner person, when they feels deprived of peace and hope or especially when they feels utterly deserted by the God, are as necessary to educate them as the bright days when joy fills them because of the divine nearness."