God chose Saint Joseph to care for the virgin Mother and to be Christ’s foster father.
Saint Joseph protected and served the Mother of God with virginal purity. He was, as Saint Bernard says, "the faithful and prudent servant whom the Lord appointed the comfort of his Mother, the foster-father of his humanity, and his chief earthly coadjutor in his great design."
Sacred Scripture expressly celebrates his goodness (Matthew 1:19) and relates the pious solicitude with which he assumed such a prominent place in the life of the Lord and the Mother of God. It is because of this pious solicitude that we invoke Saint Joseph to protect Christianity as he once protected Christ and Mary.
In addition to the March 19th feast, the Church also honors the saintly patron of workers on May 1st. And the faithful venerate him during the whole month of March.