Like I said, I would like to see a Catholic's response.
What might be another topic, I've never seen Evangelicals actually set any goalposts when they talk about Christ's finished work. What criteria has to be met in order to officially uphold his finished work? Obviously, they believe that it's still meaningful to pray, read the Bible, or witness to others despite that Christ's work is finished.
We Catholics believe that Christ's passion merited an unimaginably tremendous over-abundance of grace, far more than sufficient to atone for all the sins of everyone who has ever lived and ever will live. That is what we understand Christ's finished work to mean: that there is no need for more grace than what Jesus has already merited on our behalf. However, this over-abundance of grace must still be communicated to sinners. If all the grace out there were already fully mobilized on everyone's behalf, why doesn't everyone believe and why isn't everyone saved? We believe that we obtain grace primarily through the sacraments of the church, prayer, and good works done with the genuine desire to please God - including penance.
So, while accepting Jesus as your lord and savior does result in justification
initially, we see salvation as an ongoing rather than one-time event. That's why we believe Jesus said what he did about he who perseveres unto the end. Paul would not have said what he did in 1 Corinthians 9:27 if he believed that salvation were a one-time done deal. Romans 6 is another good example of Paul instructing Christians to seek further sanctification by serving God. Ephesians 4:15, anyone?
This is tied into the idea of divine filiation - that justification comes from infused rather than merely imputed righteousness. God does not merely cover up our sins - we are actually transformed by God's grace and, although obviously we can never attain Jesus' own level of personal righteousness, begin to share in God's own nature. The beginning of John 15 in particular mentions this clearly. We don't believe that divine filiation happens instantaneously. After initial justification through belief and baptism, charity and penance, prayer, and the sacraments are necessary to sustain and further complete and perfect the sanctification of each individual over time. There's so much throughout the New Testament that attests to this I don't know where to begin, honestly.