Some have said that the greatest difference between the Old and the New Testaments has to do with a believer receiving God's forgiveness for sin. The Hebrew word translated "forgiven" in the Old Testament only 16 times, is נסלח (nasa). However, it is also translated "to lift up" 137 times, and "to bear up" 156 times. [Is it possible that the National Aeronautics and Space Administration (NASA) could have chosen its name from this Hebrew word? But I digress.] Of the 16 times it is translated "forgiven," ten of them are in Leviticus, and all have to do with a repentant sinner bringing a sin offering to receive "forgiveness" (Lev. 4:20, 26, 31, 35; 5:10, 13, 16, 18; 6:7; 19:22). The blood of the animal for a sin offering "covered" their sin, but having one's sin "covered" is not the same thing as having one's sin forgiven.
In the New Testament Church beginning in Acts 2:1-4, 41, 47, repentant sinners received forgiveness by placing their faith and trust in the resurrected Christ. We learn from Peter's message on the day of Pentecost that David's sin was "covered" until the time God would offer His Son to provide forgiveness for him (Acts 2:25-35). God no longer requires believers to offer the blood of animals for sin (Heb. 9:1-10:23). Jesus has paid the full price for sin on the cross, for all sin from Adam's to the very last person born. Once for all! Yes, for the born-again believer, the payment for sin has already been made. However, when we sin, we grieve the Holy Spirit (Eph. 4:30), and we break fellowship with God (1 Jn. 1:3-10). By confessing our sin to God, we are restored to a "right standing" (righteousness) with Him.
A Christian, having confessed his sin and once again having a right standing with God, still has two hurdles to overcome. One is a form of pride; we find it extremely difficult to forgive ourselves. We think, "How could I do something like that? How could I have been so weak?" These questions reveal a problem with our understanding, that in us, there dwelleth no good thing (Rom. 7:18). Apparently, we suffer from the idea that we are "better than that." In reality, we think more highly of ourselves than we ought (Rom. 12:3). The Apostle Paul wrote of our struggle with our sin nature in Romans, chapter seven. Our sin may often surprise us, but instead of become disheartened, it should remind us that we have been saved by grace! We were not worthy, nor are we worthy now. As my estimation of myself decreases with each sin, my appreciation for God's gift of righteousness definitely increases!
The other hurdle is from Satan, who constantly tries to make us think we are not saved. I have heard a cute saying about how to deal with him: "The next time Satan reminds you of your past, remind him of his future!" The fact that the Hebrew word translated "forgiven" is also translated "to lift up," seems so appropriate. When we are feeling down because of our sin, the Holy Spirit works to encourage us. He wants us to walk in victory with our heads held high. Not because we are proud of ourselves, but because we know from where our righteousness comes. To God be the glory; great things He has done!