From the Simplified Catechism (church teachings)
he Grace of God’s Call
Justification comes from grace (God’s free and undeserved help) and is given to us to respond to his call.
By Baptism, the person participates in the life of the three Divine Persons because Christ (the Head of his Body) makes us adopted children of God. We receive the Spirit and henceforth call God “Father.”
This call to eternal life is supernatural, coming totally from God’s decision and surpassing all power of human intellect and will.
Sanctifying and Actual Grace
Christ’s grace (infused by the Spirit and received in Baptism) is sanctifying and deifying. “Therefore, if any one is in Christ, he is a new creation” (2 Cor 5:17).
Sanctifying grace is habitual, the permanent supernatural disposition which perfects the soul. Actual grace is God’s intervention, whether at the beginning moment of conversion or in the work of sanctification.
Making Us Collaborators
Only grace can prepare man to collaborate by faith in God’s justifying and sanctifying actions. God (who always uses our cooperation) begins “by working so that we might will it” (St. Augustine). “We are only collaborating with God, for his mercy has gone before us. It goes before so we may be called. It follows so we may be glorified. Without him we can do nothing” (St. Augustine).
God’s free action requires man to respond freely. Only in freedom can a soul enter into God’s communion. God has placed within every person a longing for truth and goodness which eternal life fulfills beyond all imagination. “If at the end of your very good works you rested on the seventh day, so we shall also rest in you on the sabbath of eternal life” (St. Augustine).
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The Spirit and His Gifts
Grace includes both the Holy Spirit himself and the Spirit’s gifts. There are sacramental graces given by each sacrament and charisms (meaning “gratuitous gift”). Whatever their nature, even extraordinary gifts such as miracles or tongues, they are meant to build up the Church.
Graces of state accompany our responsibilities both in our Christian life and in our work for the Church. “Having gifts that differ according to the grace given to us, let us use them” (Rom 12:6).
By Faith and by Fruits
Because grace is not an object of experience but is known by faith, we cannot rely on our feelings or our works to conclude that we are justified and saved (Council of Trent). However, God’s blessing in our lives shows that grace is at work. Asked about being in the state of grace, Joan of Arc responded at her trial, “If I am not, may it please God to put me in it; if I am, may it please God to keep me there.”
http://www.catholicity.com/catechism/grace.html