It is clear that the grace of the sacraments leads one to perfection. The Eucharist, states Blessed John Paul II, gives us both the power and the source of that complete gift of self. Christ gives Himself to each one of us and each one gives himself to Christ.
From Veritatis Splendor again:
21. Following Christ is not an outward imitation, since it touches man at the very depths of his being. Being a follower of Christ means becoming conformed to him who became a servant even to giving himself on the Cross (cf. Phil 2:5-8). Christ dwells by faith in the heart of the believer (cf. Eph3:17), and thus the disciple is conformed to the Lord. This is the effect of grace, of the active presence of the Holy Spirit in us.
Having become one with Christ, the Christian becomes a member of his Body, which is the Church (cf. Cor 12:13, 27). By the work of the Spirit, Baptism radically configures the faithful to Christ in the Paschal Mystery of death and resurrection; it "clothes him" in Christ (cf. Gal 3:27): "Let us rejoice and give thanks", exclaims Saint Augustine speaking to the baptized, "for we have become not only Christians, but Christ (...). Marvel and rejoice: we have become Christ! ".28 Having died to sin, those who are baptized receive new life (cf. Rom 6:3-11): alive for God in Christ Jesus, they are called to walk by the Spirit and to manifest the Spirit's fruits in their lives (cf. Gal 5:16-25). Sharing in the Eucharist, the sacrament of the New Covenant (cf. 1 Cor 11:23-29), is the culmination of our assimilation to Christ, the source of "eternal life" (cf. Jn 6:51-58), the source and power of that complete gift of self, which Jesus — according to the testimony handed on by Paul — commands us to commemorate in liturgy and in life: "As often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes" (1 Cor 11:26).
And, of course, as seen in the sections from St. John of the Cross and others, the seeking of perfection is rooted in love. Love demands perfection and perfection demands love. Such is the relationship between Christ and His Church, Christ and each one of us.
24. And so we find revealed the authentic and original aspect of the commandment of love and of the perfection to which it is ordered: we are speaking of a possibility opened up to man exclusively by grace, by the gift of God, by his love. On the other hand, precisely the awareness of having received the gift, of possessing in Jesus Christ the love of God, generates and sustains the free response of a full love for God and the brethren, as the Apostle John insistently reminds us in his first Letter: "Beloved, let us love one another; for love is of God and knows God. He who does not love does not know God; for God is love... Beloved, if God so loved us, we ought also to love one another... We love, because he first loved us" (1 Jn 4:7-8, 11, 19).
Grace leads us to love and perfection. We become like Christ through this process.
By the way, if someone is still confused as to natural law philosophy, the evil of "teleological", "consequentialist" and "proportionalist" ethical theories, and how a Catholic approaches moral issues, this encyclical provides excellent definitions and guidelines. There is much confusion among younger Catholics who have not had the advantage of good catechesis on these matters.
Take advantage of the fact that this encyclical in on line here.