The RCC, in my opinion, misunderstands salvation, justification and sanctification, getting them all jumbled up and confused.Catholics call Protestants out for failing to stress the process of justification and salvation in Scripture.
JESUS AND PETER:
The quality our your speech throughout your life will determined whether you are ultimately "justified" or "condemned (Matthew 12:37)." For Peter. "the salvation of your souls" is "the outcome of your faith (1 Peter 1:9)" only if your faith is sustained.
As born again believers ("newborn babes"), you must 'grow into salvation," not assume it is an accomplished irreversible fact.
PAUL:
Catholics agree with Eph. 2:7-8 that salvation is achieved only through grace and that "works'' can't merit salvation. So they recognize "works" as a necessary but not a sufficient condition for salvation. Thus, in its process, you must "work out your salvation" throughout your life and never take it for granted. The uncertainty of the final outcome requires you to "work out your own salvation with fear and trembling (Phil. 2:12)," because of the possibility that you might ultimately forfeit your salvation by the way you live. Even Paul must entertain the possibility that he might ultimately lose his salvation, if he is not careful: "I punish my body and enslave it, lest having preached to others, I myself might become reprobate (Greek: adokimos)." For Paul "adokimos" means becoming unsaved (Rom. 1:28). How seriously Paul takes the process of salvation is illustrated by 2 Cor. 4:16 (cp. 5:17): "our inner nature" is not simply transformed the moment we become a "new creation." Rather, it must be "made new day by day."
EPISTLE OF JAMES:
Informed Catholics recognize a truth ignored by most Protestants: In both Hebrew *"amunah" and Greek ("pistis"), the word translated "faith" also means "faithfulness." "Faith without works" cannot save you (2:14). Rather, faith must be demonstrated by a lifestyle of works (2:18). The redemptive uncertainty of the justification process necessitates a regular practice that Protestants generally ignore: "Confess your sins to one another,...so that you may be healed" (spiritually and physically--5:16).
Catholics practice regular confession to a priest to ensure confidentiality and to ensure a spiritually mature listener. Most Protestants use their belief in a once-for--justification as an excuse to trivialize the need for regular confession of sin. Their usually vague and general confessions are sporadic and are directed at God and not to other Christians as Scripture requires. Catholics think Protestants are well advised to heed Socrates' advice," An unexamined life is not worth living."
We see in Ephesians 2:4-9 that salvation is by grace alone.
We see in Romans 1 through 11 that justification (legally being guiltless) is by faith alone.
We see our sanctification in Hebrews 12 where God disciplines us as his children in refining us. These are different works of God as acts of mercy upon whom he chooses.
The RCC adds sacraments as means of human ceremony that invokes God to be gracious, as if humans can influence God. Such man-centered teaching is not in scripture, but comes from legalism created in church tradition.