St. Teresa of Avila wrote “Our Lady guards the front door of Carmel and St. Joseph guards the back door” . Here is her writings on her devotion to St. Joseph:
“Would that I could persuade all men to be devout to this glorious Saint; for I know by long experience what blessings he can obtain for us from God. I have never known any one who was really devout to him, and who honoured him by particular services, who did not visibly grow more and more in virtue; for he helps in a special way those souls who commend themselves to him. It is now some years since I have always on his feast asked him for something, and I always have it. If the petition be in any way amiss, he directs it aright for my greater good.
If I were a person who had authority to write, it would be a pleasure to me to be diffusive in speaking most minutely of the graces which this glorious Saint has obtained for me and for others. But that I may not go beyond the commandment that is laid upon me, I must in many things be more brief than I could wish, and more diffusive than is necessary in others; for, in short, I am a person who, in all that is good, has but little discretion. But I ask, for the love of God, that he who does not believe me will make the trial for himself—when he will see by experience the great good 38 that results from commending oneself to this glorious patriarch, and being devout to him. Those who give themselves to prayer should in a special manner have always a devotion to St. Joseph; for I know not how any man can think of the Queen of the angels, during the time that she suffered so much with the Infant Jesus, without giving thanks to St. Joseph for the services he rendered them then. He who cannot find any one to teach him how to pray, let him take this glorious Saint for his master, and he will not wander out of the way.”
— Teresa of Avila, Life of St. Teresa of Jesus, of The Order of Our Lady of Carmel. Chapter VI. The Great Debt She Owed to Our Lord for His Mercy to Her. She Takes St. Joseph for Her Patron.