Pride was what a third of the angels in Heaven were found guilty of when they were swept into hell. It was pride that turned Lucifer into Satan. It was pride that caused the Adam and Eve to fall from Grace and allowed death to enter into creation. Since it was Pride that closed the Gates of Heaven, It is only by the Virtue of Humilty that the Gates are reopened for Man.
1. In Paradise there are many Saints who never gave alms on earth: their poverty justified them. There are many Saints who never mortified their bodies by fasting, or wearing hair shirts: their bodily infirmities excused them. There are many Saints too who were not virgins : their vocation was otherwise. But in Paradise there is no Saint who was not humble.
Humility is not an easy virtue to obtain which is why it is necessary to have it in order to enter into Heaven.
God banished angels from heaven for their pride; therefore how can we pretend to enter therein, if we do not keep ourselves in a state of humility? Without humility, says St. Peter Damian, not even the Virgin Mary herself with her incomparable virginity could have entered into the glory of Christ, and we ought to be convinced of this truth that, though destitute of some of the other virtues, we may yet be saved, but never without humility. There are people who flatter themselves that they have done much by preserving unsullied chastity, and truly chastity is a beautiful adornment; but as the angelic St. Thomas says: “Speaking absolutely, humility excels virginity.”
Our Lady is the best example of God's earthly creation to exhibit humility. Recall Our Lady during the Annuciation, "And the angel being come in, said unto her: Hail, full of grace, the Lord is with thee: blessed art thou among women. Who having heard, was troubled at his saying and thought with herself what manner of salutation this should be. " (luke 1:28-29).
We often study diligently to guard against and correct ourselves of the vices of concupiscence which belong to a sensual and animal nature, and this inward conflict which the body wages adversus carnem is truly a spectacle worthy of God and of His angels. But, alas, how rarely do we use this diligence and caution to conquer spiritual vices, of which pride is the first and the greatest of all, and which sufficed of itself to transform an angel into a demon!
It is worthy to note that it was indeed pride that transformed an Lucifer from an angel into the devil. It was in a twinkle of the eye that Our Lord referred to the enemy of souls when he stated:
Let us take heed to always follow in the footsteps of the Church Triumphant and exercise humilty. If we can not exercise it, let us then pray for it.