"If anyone says that man can be justified before God by his own works, whether done by his own natural powers or through the teaching of the law, without divine grace through Jesus Christ, let him be anathema." (Council of Trent, canon 1)
Rome does not maintain that a man pulls himself up by his own bootstraps but speaks in terms of "cooperating with grace." In Roman Catholic theology, a person has to do good works in order to get justified in the sight of God. One keeps his right standing before Him by that same means. Rome teaches that one must attain an inherent righteousness in order to be accepted by God. However, these ideas run contrary to the teaching of Scripture.
The grace of God does not come about as a result of the doings of man (Romans 11:6). Grace and works are at odds with each other in the context of justification. Simply put, to speak of grace being infused at the moment of water baptism (which is a work) and being maintained through good works is a contradiction of terms. Paul would have understood grace to be an unmerited favor of God.
We have failed to meet the standard of moral perfection that God requires and so have incurred for ourselves condemnation (Psalm 14:2-3; Isaiah 64:6; Romans 3:9-23; Galatians 3:10). If He kept a record of our sins, we could not stand and say that we are righteous (Psalm 130:3). No one could be saved if God chose not to be merciful toward us. We do not look to ourselves for righteousness. We look to Christ alone and the righteousness that He gives to us (Luke 18:9-14; Philippians 3:3-9).
The point of contention with Roman Catholicism is not whether our lives as Christians should be characterized by obedience to God. It does not at all center around whether we perform good works. They are a display of His grace in our lives. However, good works are not to be viewed as meritorious in the sight of God. Our grounds for justification before Him is the shed blood of Jesus Christ alone (Romans 5:19).
If justification is "not of ourselves" and "not as a result of works" (Ephesians 2:8-9), then that means faith alone is the instrumental cause of justification before God. It is not obtained by both grace and works because it cannot be done that way. There are no good deeds that can save us from eternal condemnation, including those done in a state of grace. The Roman Catholic Church views grace as being necessary for salvation, but not sufficient.
Elsewhere, the Apostle Paul says, "He saved us, not on the basis of deeds which we did in righteousness..." (Titus 3:5). He continues on that thought with a stark contrast, "but according to his mercy he saved us." Thus, Paul would most definitely have condemned the sacramental system of justification taught by the Church of Rome. Some people ironically use this verse to teach that baptism is necessary for salvation, but that would be a self-contradictory interpretation.