The Spirituality of the Heart for the MSC draws its inspiration from the experience of the MSC Founders and their life centeredness on the Heart of Christ. Inspired by the Founders, the MSCs strive to make the sentiments of the Heart of Jesus their own. God's love is the center of the Spirituality of the Heart; namely, the love of the Father for all humanity as revealed in the Heart of Christ, the Incarnate Word of the Father: " The Heart of Jesus is God's love, God himself Incarnate. God is love." The pierced heart of Christ on the cross (Jn 19:34, 37) reveals to us how much God loves us (1 Jn 4:9, 10).  
Since God has loved us first we are bound to love one another. To respond to God's love is not only that we should love God, but rather that we should love one another (1 Jn 4:11).  The sign and proof of our love for God is our love for one another (1 Jn 4:20-21). In the first epistle of St. John, like in the letter of St. Paul to the Romans (Rom 5:8), it is stressed that God loved us first (1 Jn 4:10, 19), and showed this love in sending his Son into the world, so that we might have life (1 Jn 4:9). "In this is love, not that we loved God but that he loved us and sent his Son to be atoning sacrifice for our sins. Since God loved us so much, we also ought to love one another" (1 Jn 4:10-11). Thus the MSC Founders understood that God's divine love is the basis for loving our neighbours. 
As emphasized in Perfectae Caritatis (Vatican Council II):
They who make profession of the evangelical counsels should seek and love above all else God who has first loved us (cf. 1 Jn 4:10). In all circumstances they should take care to foster a life hidden with Christ in God (cf. Col 3:3), which is the source and stimulus of love of the neighbor.  (PC 6).
Fr. Chevalier experienced the depth of God's love revealed in Jesus Christ and his own limitation in responding to this love. Therefore, he emphasized the need of conversion in our lives. Every person is invited to a change of heart, to a new heart and to believe in God's merciful love. Jesus Christ urges us to change our life. Return into yourself, He tells us through His prophet. "Sinners, return to your heart." (Is 46:8) We should make ourselves a new heart by changing our sentiments. "Make yourself a new heart." (Ez 18:31).   Based on this text of Fr. Chevalier, the MSC sisters find inspiration in the word of St. Augustine in his Confessions: "Return to your own heart and abide in Him that made you."  It is a confirmation of the need to encounter God in one's own heart, to experience God's love within one's own life. In this sense, a Spirituality of the Heart is a way of speaking symbolically about one's inner-life and its relationship with one's outer-life.   For the MSC, the interior life of Christ penetrates the depths of one's heart and challenges us to live and love as Christ did. For that reason, Fr. Linckens has emphasized that the dispositions of Christ are the pattern for our spiritual life.
Fr. Eugene Cuskelly, a former Superior General of the Missionaries of the Sacred Heart, summarizes the meaning of the Spirituality of the Heart as follows:     
•We have to go down to the depths of our own soul in a realization of our profound personal needs
of life, of love and of meaning;
• We must find through faith and reflection, the answer to our own questioning in the Heart of
Christ, in the depths of his personality, where man's yearning and God's graciousness meet
in redemptive incarnation;
  • Then, fashioned by these forces, our own heart will be an understanding heart, open to, feeling for, and giving to our brothers and sisters in Christ;
  • We will not be disheartened, or discouraged in the face of difficulties.
  • We follow Christ who "loved with a human heart" as Vatican II reminds us:
“He shared our humanness that we might know that over us all is the everlasting love of God.
In God's good time, the omnipotent love of God will have its way. It is this love in which we have learned to believe."
The Spirituality of the Heart, therefore, begins with the discovery of the depth of our own hearts. It presents to us the Heart of Christ as the ultimate answer to our deepest yearnings. It calls us to a conversion, to a change of heart, to open our hearts to be molded after His Heart. The Spirituality of the Heart, then, challenges us not to be disheartened in the face of difficulties because Christ has already given the ultimate answer to all our difficulties.   
In a similar manner, Vatican Council II has emphasized to the Church that:
“Every one of us needs a change of heart; we must set our gaze on the whole world....  The Church, however, living in the midst of these anxieties, even as it makes these statements, has not lost hope. The Church intends to propose to our age over and over again, in season and out of season, the apostle's message: ‘Behold, now is the acceptable time’ for a change of heart; ‘behold, now is the day of salvation’.” (Gaudium et Spes 82). The Spirituality of the Heart, then, leads us to change our relationships with others. It leads us to listen to the heart of the world. It leads us necessarily to action because "the love of Christ urges us" (2 Cor 5:14).