"God alone satisfies."
Saint Thomas Aquinas, O.P
"And Jesus, looking upon him, loved him." This is the love of the Redeemer: a love that flows from all the human and divine depths of the Redemption. This love reflects the eternal love of the Father, who "so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life." The Son, invested with that love, accepted the mission from the Father in the Holy Spirit and became the Redeemer of the world. The Father's love was revealed in the Son as redeeming love. It is precisely this love that constitutes the true price of the Redemption of man and the world.... The call to the way of the evangelical counsels springs from the interior encounter with the love of Christ, which is a redeeming love. Christ calls precisely through this love of His. In the structure of a vocation, the encounter with this love becomes something specifically personal. When Christ "looked upon you and loved you," calling each one of you, dear religious, that redeeming love of His was directed towards a particular person, and at the same time it took on a spousal character: it became a love of choice. This love embraces the whole person, soul and body, whether man or woman, in that person's unique and unrepeatable personal "I." The One who, given eternally to the Father, "gives" Himself in the mystery of the Redemption, has now called man in order that he in his turn should give himself entirely to the work of the Redemption through membership in a community of brothers or sisters, recognized and approved by the Church....Yes, Christ's love has reached each one of you, dear brothers and sisters, with that same "price" of the Redemption. As a consequence of this, you have realized that you are not your own, but belong to Christ. This new awareness was the fruit of Christ's "loving look" in the secret of your heart. You replied to that look by choosing Him who first chose each one of you, calling you with the measurelessness of His redeeming love. Since He calls "by name," His call always appeals to human freedom. Christ says: "If you wish...." And the response to this call is, therefore, a free choice. You have chosen Jesus of Nazareth, the Redeemer of the world, by choosing the way that He has shown you."                                                                                                                                           from Saint  John Paul II's  Redemptionis Donum

Saint John Paul II on Vocations