We believe that we are conformed to the image of Christ primarily through the sacraments.
Baptism
Holy Baptism is the basis of the whole Christian life, the gateway to life in the Spirit (vitae spiritualis ianua),4 and the door which gives access to the other sacraments. Through Baptism we are freed from sin and reborn as sons of God; we become members of Christ, are incorporated into the Church and made sharers in her mission: "Baptism is the sacrament of regeneration through water in the word."5 (CCC 1213)
Confession
Christ instituted the sacrament of Penance for all sinful members of his Church: above all for those who, since Baptism, have fallen into grave sin, and have thus lost their baptismal grace and wounded ecclesial communion. It is to them that the sacrament of Penance offers a new possibility to convert and to recover the grace of justification. The Fathers of the Church present this sacrament as "the second plank [of salvation] after the shipwreck which is the loss of grace."4 (CCC 1446)
Eucharist
"The Eucharist is the efficacious sign and sublime cause of that communion in the divine life and that unity of the People of God by which the Church is kept in being. It is the culmination both of God’s action sanctifying the world in Christ and of the worship men offer to Christ and through him to the Father in the Holy Spirit."138 (CCC 1325)
You may want to take a look at the catholic understanding of the stages of the spiritual life.
This page on newadvent is a good introduction:
newadvent.org/cathen/14254a.htm
Furthermore, I recommend that you take a look at “The Way of Perfection”
by St. Theresa de Avila