When it comes to the Mother of God, the Catholic Church honors Mary with many titles, prayers and devotions. During the liturgical season of Ordinary Time, priests, deacons, seminarians, consecrated men and women and the laity conclude the final hour of the Liturgy of the Hours, Compline (Night Prayer), with a hymn to Mary—the Salve Regina (Hail Holy Queen). Another common devotion, the rosary, traditionally ends with the Hail Holy Queen, in which we hail Mary as the Mother of Mercy, our Life, our Sweetness and our Hope, accompanied with a litany of other titles. If you are like me and other Catholics, on occasion you might rattle off this prayer from memory without giving a thought to the meaning of the words being prayed. These attributes of Mary can be perplexing when one actually contemplates their meaning.
Recently, a friend posed the following question to me: Why do we call Mary our life, our sweetness and our hope? To answer this question, I turned to one of the doctors of the Church, St. Alphonsus Liguori, who wrote an explanation of the Salve Regina in his monumental work The Glories of Mary.  St. Alphonsus identifies two reasons as to why Mary is our life. Mary is our life because she obtains for us the pardon of our sins and because she obtains for us perseverance. Mary is our sweetness because she renders death sweet to her clients. And lastly, Mary is the hope of all, including sinners. These three attributes accorded to Mary in the Salve Regina are best summarized by the Hail Mary.
At the conclusion of the Hail Mary, one prays: Holy Mary, Mother of God, pray for us sinners, now and at the hour of our death. In the Hail Mary we ask Mary to be our life, our sweetness and our hope, because we ask for her continual intercession. Mary becomes our life when we ask her to pray for us, because through Mary, grace is given to the devotee and thus to the entire world.  When a Christian lacks devotion to the Mother of God, St. Alphonsus notes the soul “is immediately enveloped in darkness.”  Due to Mary’s continual role of intercession for her faithful children, the absence of devotion leads to a privation of grace, which was at one time being supplied by Marian devotion. A lack of Marian devotion leads to the non-reception of particular graces on the part of the devotee. A healthy Marian devotion provides the soul with life because grace is supplanted to continue on the path toward virtue and Christian perfection.
When praying the Hail Mary, the devotee keeps death before his or her eyes. We are able to call Mary our sweetness because we have confidence in that prayer, “pray for us now and at the hour of our death.” St. Alphonsus recounts stories of individuals who, at their death, experienced great temptation which could have resulted in the loss of grace at the hour of death, however, each time, the soul was able to persevere and taste the sweetness of death because of Mary’s intercession at their final moments. Sweetness of death is granted to the devotee because a person’s confidence in their prayer to Mary. Mary will take the soul of her dying servant to its eternal destiny because of his or her faithfulness. This notion is supported by other private revelations in which certain promises were entrusted to certain visionaries.  Through devotion to and the intercession of the Mother of God, the faithful who honor Mary are granted the grace of tasting the sweetness of death and by the grace of God will remain faithful until their last breath, even amid spiritual warfare.
In the third salutation, hope, we find that Mary provides hope for the Christian who honors her because of her role as a dispenser of grace contained within her identity as a spiritual mother. Since Mary was a human being, (albeit immaculately conceived), Mary gives the ordinary Christian a goal to strive toward in life. Mary becomes a model on which the Christian can model his or her life by emulating the virtues of Mary.  Lastly, the prayer of Mary aids in the conversion of sinners  because she is the refuge of sinners—their only hope and advocate  outside of Christ. By praying for and obtaining the conversion of sinners, a sinner is then afforded the hope of eternal life rather than eternal damnation.
St. Bernard of Clairvaux in his homily, In Praise of the Virgin Mother, provides an exhortation to the members of his monastic community to call upon Mary in the time of their sin. That passage best summarizes why it is appropriate and fitting for us to call Mary our life, our sweetness and our hope. Bernard writes:
If you do not want to founder in the tempest, do not avert your eyes from the brightness of this star [Mary]. When the wind of temptation blows up within you, when you strike upon the rock of tribulation, gaze up at this star, call out to Mary. Whether you are being tossed about by the waves of pride or ambition or slander or jealousy, gaze up at this star, call out to Mary. When rage or greed or fleshly desires are battering the skiff of your soul, gaze up at Mary. When the immensity of your sins weighs you down and you are bewildered by the loathsomeness of your conscience, when the terrifying thought of judgment appalls you and you begin to founder in the gulf of sadness and despair, think of Mary. In dangers, in hardships, in every doubt, think of Mary, call out to Mary. [. . . .] Following her, you will never go astray. Asking her help, you will never despair. 
In the Christian life, temptation will come, but if one turns to Mary, one will not go astray, for she will help the sinner. She is the ‘Star of the Sea’ who guides the Christian on his or her pilgrimage to the Heavenly Jerusalem in spite of life’s trials and tribulations. Because she is the trusted pedagogue, she leads the Christian to life by her intercession and dispersal of grace; she is the Christian’s sweetness because by her continual intercession she can help the devotee in his or her final hours; and she is the hope of Christians because by turning to her Christians are able to remain faithful to Christ. Mary is the antidote to temptation in whom one finds hope of perseverance in the state of grace until the end. 
Jesus Christ is the Way, the Truth, and the Life. His Mother, who was chosen by the Eternal Father to be the mother of His Son, was granted certain privileges in her life which allowed her to become the mother of all the living. The privileges granted to Mary allow her to rightly be called our life, our sweetness and our hope. By means of Mary, the Life, par excellence, was brought into the world, allowing all Christians the opportunity to participate in the Divine Life offered by God. Mary is an instrument who leads Christians to the one who is the source of all Life—Jesus; Mary also leads Christians to the sweetness of unity with her Son, and finally, Christians are able to find their ultimate hope fulfilled in Jesus Christ; all is possible through the mediation of Mary. As the celestial moon, Mary reflects Christ, bringing all Christians to the source of all life, sweetness, and hope—He who is the Sun, Jesus Christ.
 St. Alphonsus de Liguori, The Glories of Mary edited by Rev. Eugene Grimm (Brooklyn: Redemptorist Fathers, 1931). N.B. The version cited herein is distributed by Our Blessed Lady of Victory Mission based out of Milwaukee.
 Many saints and theologians of the Church throughout the centuries have maintained that God wills grace to come to us through the intercession of Mary (c.f. Liguori, 191). Some theologians advocate for a fifth Marian dogma which includes the title “mediatrix of all graces.” Since the Second Vatican Council, the Church has preferred to use caution with the usage of this phrase; instead the Church prefers the role of Mary as a spiritual mother, of which the doctrine of Mary as mediatrix of all graces is contained therein.
 Liguori, 111.
 Such examples include the fifteen promises to those who pray the rosary daily (given to Blessed Alan de la Roche) and the Sabbatine privilege attached to the wearing of the scapular when the conditions are faithfully lived by the devotee.
 By looking to the scriptures we find Mary to be a woman of prayer and service who had complete trust in God’s divine providence. The Church also has a devotion to the Ten Evangelical Virtues of Mary which honor Mary for being most pure, most prudent, most humble, most faithful, most devout, most obedient, most poor, most patient, most merciful and most sorrowful.
 Liguori, 147.
 Liguori, 148.
 Bernard of Clairvaux, “Four Homilies in Praise of the Virgin Mother” in Magnificat, trans Marie-Bernard Said, with an Introduction by Chrysogonus Waddell (Kalamazoo: Cistercian Publications Inc, 1979), II.17.
 St. Alphonsus notes that in a revelation to St. Bridget, if Lucifer would humble himself, Our Lady could obtain the grace of his conversion. If Mary could obtain the grace of Lucifer’s conversion, she can surely obtain the conversion of sinners through her prayers if the person is humble enough to request Mary’s assistance. C.f. Liguori, 155.