St. John of the Cross
Ascent of Mount Carmel
Book the Third › Chapter XXVIII · Part 2 of 2
9. The seventh evil is that, in so far as a man stifles not vain rejoicing in moral works, he is to that extent incapable of receiving reasonable counsel and instruction with regard to good works that he should perform. For he is lettered by the habit of weakness that he has acquired through performing good works with attachment to vain rejoicing; so that he cannot consider the counsel of others as best, or, even if he considers it to be so, he cannot follow it, through not having the necessary strength of mind. Such persons as this are greatly weakened in charity toward God and their neighbour; for the self-love with respect to their good works in which they indulge causes their charity to grow cold.
Source: Ascent of Mount Carmel (CCEL)