Venerable Macarius of Optina. "Edifying Teachings" (from letters).
You also write that you do not see vanity and pride in yourself and would like to know the signs of these. The very fact that you do not notice these passions in yourself is a sign that they wrap your soul, covering it with darkness and gloom, which, both in visible objects and in mental ones, equally prevent you from seeing what is present. There is clear evidence of this in the 23rd Step of the Ladder, how the wise elder taught spiritually his brother not to be proud, and he, blinded in his mind, answered: forgive me, father, I have no pride. The elder continued: yes, child, how can you prove your pride more than with these words that “I have no pride.” Darkness, according to Basil the Great, is the absence of light. And in spiritual things, in the absence of the light of humility, the darkness of pride covers the soul (I, 446, 755).
When one does not notice anything bad in oneself, isn’t he led by the spirit of pride? But the humble see their sins like the sand of the sea (V, 145, 240).
I heartily rejoice at the change in your disposition, that is, keeping away from laughter, idle talk and blasphemy; but you should control that with it, arrogance, vanity, conceit and the most fierce pride do not creep into the heart, which blind the person and do not allow “to see one’s sins” and “to have a contrite and humble heart” (III, 280, 498).