In one of his sermons on St. Joseph, St. Bernardine of Siena declares: “It is a general rule regarding all special graces communicated to a rational creature that when Divine Grace chooses someone for some special office or some very exalted state, it gives all the charisms needed by the person chosen,  and that he is given them profusely. This is accomplished eminently in the person of St. Joseph.”  Such was the earth which received grace in the soul of St Joseph, that it bore abundant fruit in the virtues which adorned his soul. Thus St. Joseph is a model of virtue: a just man, obedient, magnanimous, faithful, humble, poor, a holy spouse, an exemplary father, a lover of silence, a worker, generous, with a spirit of great sacrifice… and much more, but the most notable virtues are purity and chastity. God did not only choose a virgin to be the Mother of His only-begotten Son, but it was also most fitting that the father be pure and chaste as well.
Perhaps someone might ask why we have a special devotion to St. Joseph. St. Bernardine of Siena gives us the answer: “If Holy Church is indebted to the Virgin Mother, for it was by her that the Church was made worthy to receive Christ, certainly the Church is also indebted to St. Joseph, after Mary, regarding gratitude and singular veneration.”  The liturgy itself places him immediately after the Virgin Mary. Moreover, St. Joseph is an eminent member of the Church of Christ, a model of virtue, the patron of the Universal Church, the patron of a holy death, the Spouse of Mary, the Father of the Incarnate Word, to whose care the Redeemer himself was subjected. But above all we have a special devotion to him because of his most efficacious intercession, which we have experienced many times.
St Teresa testifies to St Joseph’s care and the power of his intercession: “And I took as my advocate and patron the glorious St. Joseph, and I often recommended myself to him. I saw clearly that inasmuch as in such a need as in other greater ones, like loosing one’s good name or one’s soul, this father and lord of mine freed me more greatly than how I knew to ask. To this day I do not remember asking for anything that he did not give me... I have experienced that this great saint comes to our aid in all things, and that the Lord wants us to understand that just as to St Joseph He was submitted on earth, for he bore the name of Father and being His guardian, he could command Him, in the same way He does what he asks... I believe that it has already been some yearsthat I asked him for something on his feast, and I always saw it accomplished. If the petition was something faulty, he corrected it for my greater good.” 
In the same way that God gave His Son the best parents, who were both chaste, He also willed for His Son to have a chaste spouse, as is each consecrated woman. And each religious, chosen for and with a singular love to be a spouse of the Incarnate Word, must totally dedicate herself to caring for Him by imitating St. Joseph; that is, to please Him by doing His most holy will and by being spiritual mothers of His children.
“Recalling that God entrusted the first mysteries of the salvation of men to the faithful custody of St. Joseph, ask Him that you may collaborate faithfully in the work of salvation, that He give you a pure heart like St Joseph, who gave himself entirely to serve the Word Incarnate, and that “through the example and the intercession of St. Joseph, faithful and humble servant, we may always live consecrated in justice and holiness.” 
A verse of a hymn to St. Joseph says:
“O Guardian of Jesus in His divine infancy
Protect the life of grace in childhood.
Let us sing to Joseph, guardian of our faith,
The Redeemer Himself chose him as His Father.”
St. Joseph is “he to whom God ‘entrusted the custody of His most precious treasures’”, that he might protect them with his tireless care.