Dear Brothers and Sisters in Christ Jesus,
We at times find ourselves asking the question: “What must I do to be saved?” “The promise of eternal life is a gift, freely offered to us by God (CCC 1727). Our initial forgiveness and justification are not things we “earn” (CCC 2010). Jesus is the mediator who bridged the gap of sin that separates us from God (1 Timothy 2:5); he bridged it by dying for us. He has chosen to make us partners in the plan of salvation (1 Corinthians 3:9).
The Catholic Church teaches what the apostles taught and what the Bible teaches: We are saved by grace alone, but not by faith alone (which is what “Bible Christians” teach; see James 2:24).
When we come to God and are justified (that is, enter a right relationship with God), nothing preceding justification, whether faith or good works, earns grace. But then God plants his love in our hearts, and we should live out our faith by doing acts of love (Galatians 6:2).
Even though only God’s grace enables us to love others, these acts of love please him, and he promises to reward them with eternal life (Romans 2:6-7, Galatians 6:6-10). Thus good works are meritorious. When we first come to God in faith, we have nothing in our hands to offer him. Then he gives us grace to obey his commandments in love, and he rewards us with salvation when we offer these acts of love back to him (Romans 2:6-11, Galatians 6:6-10, Matthew 25:34-40).
Jesus said it is not enough to have faith in him; we also must obey his commandments. “Why do you call me ‘Lord, Lord,’ but do not do the things I command?” (Luke 6:46, Matthew 7:21-23, 19:16-21). We do not “earn” our salvation through good works (Ephesians 2:8-9, Romans 9:16), but our faith in Christ puts us in a special grace-filled relationship with God so that our obedience and love, combined with our faith, will be rewarded with eternal life (Romans 2:7, Galatians 6:8-9).
Read the letters of St. Paul to the Christian communities and see how often Paul warned Christians against sin! He would not have felt compelled to do so if their sins could not exclude them from heaven. Paul reminded the Christians in Rome that God “will repay everyone according to his works: eternal life for those who seek glory, honor, and immortality through perseverance in good works, but wrath and fury to those who selfishly disobey the truth and obey the truth and obey wickedness” (Romans 2:6-8).
Sins are nothing but evil works (CCC 1849-1850). We can avoid sins by habitually performing good works. Every saint has known that the best way to keep free from sins is to embrace regular prayer, the sacraments (the Eucharist first of all), and charitable acts. (Pillar of fire-Pillar of truth, Catholic Answers.)