Greetings,
You asked: If I understand correctly, a Catholic loses his salvation if he commits a mortal sin.
Response: Catholics do not tend to use the word 'salvation' in the same way as you are using it. We recognize there is imminent salvation in the Gospel of John, and in some quotes of Paul, and we do not deny the concept. However, we tend to use the word salvation for end times. What happens to a person after they are judged. If they go to heaven they are saved. If they do not go to heaven they are NOT saved. We do not talk about loosing and gaining 'salvation'.
The language that a catholic uses is what is my current relationship with God in his Son Jesus Christ. Either a person is "In the State of Grace", or the are "Not in the State of grace". Being in the state of grace is the equivilent of how you would use the word saved. (I hope this clarification of terms makes sense).
If a person is in a state of Grace they are filled with the Holy Spirit, and are in the fulness of Sonship of adoption calling out Abba, Father. However, we can rupture our relationship with God so badly that we ourselves reject God's grace. Even though he continues to love us and call us, we, through our choice/actions have denied God, and we have broken the relationship. In this case we are no longer in the state of grace. Example: If person became an atheist, they are denying God, and cut themselves from the Grace of God.
You then said: If he confesses that sin to a priest, he regains his salvation?
Response: The normal means of reconciling with God according to the Catholic Church after initial justification of faith, repentance, Baptism, is the Sacrament of Penance. Of course, we are all called to repent and constantly turn to God, this much we can agree to. However, where we would disagree is this: Catholics Read John 20:20 as the disciples given the authority to forgive sin(Actually, it the power of the Holy Spirit which was given to them that forgives the sin, but uses the priest as the means). So the person confesses and the priest absolves. It is a way for Christ to continue to act in the world, but he acts through the priest. After Confession, the person is restored to a state of Grace.
You ask: Does he lose his salvation every time he commits a mortal sin, and regain salvation everytime he confesses to a priest?
Response: Totally severing your relationship with God through Mortal sin is more difficult than you think. It is not a daily, in and out of the state of grace. A person never has to commit mortal sin.
Also, confession is the normal means of reconciling with God. However, if you are alone and there is no possible way to get to confession. You can be forgiven by making a perfect act of Contrition(sorrow for your sins) on the condition that you will go to confession when you are able.
You asked: Is this an accurate understanding of Catholic salvation?
Response: Actually it is only a small part of salvation and grace. We never even spoke of the need for Faith, hope and love, the need for the Grace of God to permeate our life as gift. All of those aspects are Very important.
You: If so, it seems as if the Catholic teaching of salvation is entirely based on works.
Reponse: Actually no. Works is when you earn heaven like a paycheck. It is trying to Obligate God into giving you heaven. NOBODY can obligate God to do anything. However, God will keep his promises when he gives them. Forcing an obligation on God is where works comes in(God I did this so you OWE me).
peace
