One of the Bible's greatest truths is that when we put our trust and faith in Jesus Christ, God forgives all of our sins -- without exception. The Bible says, "He forgave us all our sins" (Colossians 2:13).
This includes even the sins we can't remember. After all, none of us can remember every sin we ever committed; we even might not have been aware of them at the time. But God knows all about them, and the Bible assures us that even the sins we've forgotten about or didn't realize we were committing were placed on Christ, and He died for them all. The Psalmist said, "You have set our iniquities before you, our secret sins in the light of your presence" (Psalm 90:8).
Don't let your past sins weigh you down. Instead, thank God every day that Christ has taken them away, and you now belong to Him. Thank Him too that even when you were far away from Him, He still was watching over you and preserving your life. Thank Him, as well, for His presence with you every day.
In addition, let the truth of God's Word, the Bible, penetrate your life every day. Satan will try to discourage and accuse you, but God's truth frees us from his lies. Ask God also to use you in the lives of others, pointing them to Jesus Christ and His power to save.