Agree that God does move us to repentance.
However, John 20:21-23 has nothing to do with the roman catholic confessional booth or having to confess your sins to a priest. That is not evidenced in the NT church.
The Greek in 1 John, and the NT for that matter, tells us that if we believe Jesus is the Son of God, we do indeed have eternal life.
This false doctrine of mortal sins is not supported by the NT nor is the concept of purgatory and penance.
If there is any "work" we can do to prove our worthiness before God, the cross is nullified.
This passage from Colossians addressings exactly what Christ did for us when He died on the cross.
13When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, 14having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross. Col 2:13-14 NASB
As the certificate of debt is cancelled out the roman catholic concept of purgatory where we go to "get cleaned up" is voided.
but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin. 1 John 1:7 NASB
The blood of Christ either cleanses us from all of our sins or it doesn't.
The secure position of the believer is further made clear by Paul in Ephesians where he writes:
7In Him we have redemption through His blood, the forgiveness of our trespasses, according to the riches of His grace 8which He lavished on us. In all wisdom and insight 9He made known to us the mystery of His will, according to His kind intention which He purposed in Him 10with a view to an administration suitable to the fullness of the times, that is, the summing up of all things in Christ, things in the heavens and things on the earth. In Him 11also we have obtained an inheritance, having been predestined according to His purpose who works all things after the counsel of His will, 12to the end that we who were the first to hope in Christ would be to the praise of His glory. 13In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, 14who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory. Ephesians 1:7-14 NASB
The astute reader will note our redemption is through His blood, we have forgiveness of our trespasses, we have an inheritance, after believing in Him, we are sealed by the Spirit, who is given as a pledge of our inheritance.
There is no good deed or work we can do to earn our salvation much as the roman catholic wants there to be.
Keep that word in mind: mortal. It means death. Mortal sins are deadly sins because they kill off this supernatural life, this sanctifying grace. Mortal sins can’t coexist with the supernatural life, because by their nature such sins are saying “No” to God, while sanctifying grace would be saying “Yes.”
This is yet another falsehood by the roman catholic church. Paul wrote "23for all have sinned and fall short of the glory of God, 24being justified as a gift by His grace through the redemption which is in Christ Jesus; 25whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed; 26for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus. Rms 3:23-26 NASB
Paul notes everyone...including Mary, has sinned. There are no exceptions save Christ of course.
Later in Romans 6:23 Paul wrote "the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord."
Paul did not say, the wages of mortal sin, is death. He indicates all sin leads to death.
The catholic belief you can have the "little sins" or venial sins which don't have to be confessed to remain in fellowship with God, and still be right with God, shows a lack of understanding of sin. It goes back to a works based mentality which is rejected by the NT.
All sin separates us from God apart from faith in Christ.
The doctrine of purgatory, or the final purification, has been part of the true faith since before the time of Christ. The Jews already believed it before the coming of the Messiah, as revealed in the Old Testament (2 Macc. 12:41–45) as well as in other pre-Christian Jewish works, such as one which records that Adam will be in mourning “until the day of dispensing punishment in the last years, when I will turn his sorrow into joy” (The Life of Adam and Eve 46–7). Orthodox Jews to this day believe in the final purification, and for eleven months after the death of a loved one, they pray a prayer called the Mourner’s Kaddish for their loved one’s purification.
The appeal to Orthodox Jews again shows a works based mentality on the part of the roman catholic as the Orthodox do not believe Jesus is the Messiah.
But you may be on to something as it does not appear that many roman catholics have complete faith in the forgiveness of Christ through His shed blood which may also explain the roman catholic appeal to Mary for so much.
Peter, however, captures what Christ did for us on the cross and what belief in Him actually does for the believer.
24and He Himself bore our sins in His body on the cross, so that we might die to sin and live to righteousness; for by His wounds you were healed. 25For you were continually straying like sheep, but now you have returned to the Shepherd and Guardian of your souls. 1 Peter 2:24-25 NASB
Other versions say *freely by His grace*.
In the Greek, the word freely* is this.
http://biblehub.com/greek/1432.htm
dórean: as a gift, to no purpose
Original Word: δωρεάν
Part of Speech: Adverb
Transliteration: dórean
Phonetic Spelling: (do-reh-an')
Short Definition: as a free gift, without payment, freely
Definition: as a free gift, without payment, freely.
HELPS Word-studies
Cognate: 1432 dōreán(the adverbial form of 1431/dōrea) – something freely done (as gratis), i.e. without "cause"; unearned (undeserved); freely given (without cost) hence not done out of mere obligation or compulsion. See 1431 (dōrea).
FREELY given.
Not attained by going to confession and doing penance to earn it or become worthy of it>
FREELY forgiven by God's grace.
Without strings.
The Catholic requirements to attain forgiveness make it a work and hence wages due.
If you do *X* then God does *Y*. By our doing it, it makes God beholden to us for what we did and then He is obligated to *forgive* us.
But that's not forgiveness.
Forgiveness by it's very nature is not earned or deserved. If it was, once again, it's wages due for works performed.
It ceases to be forgiveness but an obligation.