colossians 2:13-15
13 And you, who were dead in your trespasses and the uncircumcision of your flesh, God made alive together with him, having forgiven us all our trespasses, 14 by canceling the record of debt that stood against us with its legal demands. This he set aside, nailing it to the cross. 15 He disarmed the rulers and authorities and put them to open shame, by triumphing over them in him.
The record of debt that stands between us and God was nailed to the cross when Jesus died. This disarms our enemy, when he tries to bring up things that we have done to discourage us and make us feel guilt or shame. The cross gives us humble confidence to come before God. We come confidently because we know that all our sin has been dealt with by Jesus and we come humbly because we know it's not based on our list of accomplishments (or lack of them!) but based on what Jesus has done.