“Work out your salvation with fear and trembling” - Phil 2:12
The Bible also tells us to confess our sins to one another. And for Catholics, who better than the priest who can act as spiritual director and counselor. Also, Catholics believe the priest can forgive sins because of the ability to do so bestowed upon the apostles by Jesus to forgive sins (John 20:23). This “ability” is also given from the apostles to the Bishops, and even to the presbyters (priests). So, when in confession, Jesus is forgiven the sins through the priest.
Mass is worship. Why go to church? “Where two or more are gathered in my name, I am there with them” (Matt 18:20)
Gathering together to worship has been a fundamental part of Judaism and has continued into Christianity. Why go to church? Because Jesus is there! And what better way to worship than to gather together at the same time and raise our voices together!
Works are necessary for salvation because a faith without works is a dead faith (as good as no faith at all). Good works are necessary as a testament or proof of having a living faith. For it is by a living faith that we can receive the graces necessary to be saved, for we are saved by grace through faith (a living faith). The faith and works are inseparable. Works alone cannot save, but neither can faith alone. Only a living faith made evident by works has the ability to save. And a living faith is only possible by doing good works, that is, works commanded by Jesus. “If you love me, keep my commandments” (John 14:15) and “If you keep my commandments, you will remain in my love” (John 15:10) And goes on to mention about feeding the hungry, clothing the naked, etc.
If we obey Jesus’ commandments, we maintain his grace that is given to us. By sinning, we reject that grace, and cannot be saved unless we repent.
More about confession and the forgiveness of sins
More about Grace
More about faith and works