Sin does separate us from God. That’s why we need a Savior. Jesus died so our sins could no longer keep us out of God’s presence. Even after we’re saved we still sin, so Jesus had to die for all our sins, past present and future, and that’s what He did.
Colossians 2:13-14 says Jesus forgave all our sins at the cross. That word “all” means each and every one.
Hebrews 10:12-14 says by His once for all time sacrifice He has made us perfect forever, and 2 Cor. 5:17 tells us that anyone who is in Christ is a new creation. The old has gone, the new has come. The righteousness we have now comes from God through our faith in Jesus (Romans 3:21-24).
After we’re saved we should still confess when we sin so that God can purify us again (1 John 1:9), but our initial decision to accept the Lord’s death as payment in full for all the sins of our life is all that’s needed to assure our place in heaven (Ephesians 1:13-14).
This does not mean we’re free to sin whenever we feel like it. Personally, I don’t know of any believers who feel that way about sinning, because we all want to behave in a way that pleases the Lord out of gratitude for our salvation. But no one is perfect and we all sin in spite of ourselves. When we do we confess, and when we confess the Lord will immediately forgive us, and it will be like it never happened.
Blessed is the one whose transgressions are forgiven, whose sins are covered. Blessed is the one whose sin the Lord does not count against him and in whose spirit is no deceit (Psalm 32:1-2).