As already explained...it's in the Bible. Think about it. Jesus taught repentance for the forgiveness of sins. In the Catholic faith, we turn away from that sin, replacing it with obedience. We confess the sin, we, by God's grace, are forgiven the sin, and also by God's grace we do the good works he planned in advance for us to do. By his grace, we are justified. All of this is Biblical and Apostolic tradition. This is the way of our worship and our glorifying God.
Your way of worshiping and glorifying God is by believing by Christ's work, your soul, yet to be born, no matter how great its sins, are already justified by God due to the fact Christ' blood is justified and his blood covers all your sins, past,present, future.
I've said on this forum many times: When it comes to others beliefs and worship, we are on holy ground.
As I set forth, Catholic belief includes many Biblical teachings.
As I set forth, your denomination focuses on one.
Both these are holy ground, and when it comes to worship and glorifying God, who am I to desecrate your denomination's worship and glorification of God--and by the same token, who are you to desecrate Catholic worship and glorification of God?