Another Interesting Quote from Fr. Dubay's Book...
"Through the long centuries of the Christian dispensation spiritual directors have considered humility as an important sign of authenticity. When St. John of the Cross was asked his opinion of a nun who reportedly had extraordinary experiences, his analysis of her written account was negative because indications of humility were lacking. She had, he said, little fear of being mistaken. She was overly confident of her opinion. Where this healthy fear is absent, remarked the saint, the Spirit of God is never present. She seemed to desire to persuade others of the goodness of her experiences; she gave little evidence of humility and her style lacked simplicity -- it was exaggerated and affected. The saint was consequently little impressed with her experiences.
In the concrete order humility shows itself as a sign of the Spirit's operation in several ways. It appears in the desire to be corrected. It shows itself in the avoidance of the self-focusing of illuminism. The humble person can be reached by objective evidence because he does not consider himself a privileged channel from the Holy Spirit to the human race. It is a chilling experience to meet face to face with a person so supremely sure of his inner light and his interpretation of the Bible that he rejects not only what you say but also what exegetes and theologians and saints say. He rejects these interpreters, unaware that he is setting himself up as the interpreter per excellence.
This humility sign is seen in obedience to one's legitimate superior and to one's spiritual director. This person has no problem about submitting his will to that of another. The humble individual is willing to be sent. He is not a self-originating oracle. If he is the recipient of a genuine divine communication, he still obeys his leaders if they think otherwise."
Catholic Encyclopedia on Humility
What St. Thomas Aquinas has to say about humility