Repent means to change your mind. Before you were saved, you thought x. Maybe x was that you were a pretty good person who made a few mistakes.
But here God is, telling you that no, you were in fact dead and needed to become a living being. That you were not "good" because only God is good. And that those mistakes were so heinous that it required the death of God to fix.
So you changed your mind, which is repented, and sided with God. You agreed with God that you were a sinner in need of a savior, and that He would save you if you asked Him to.
By confessing out loud that He is Lord, and by believing in your heart God raised Him from the dead, you were saved. You were born again in the Spirit, and became a new creation.
However, your maturity as a Christian has been stunted by the devil who keeps accusing you of being a sinner. That's what he does, 24/7. He constantly reminds you of all of your sin, and how loathsome you must be to God.
As always, he lies.
When the Father sees you, He sees Jesus. And as Jesus is in heaven, so are you here on this earth.
You're drinking milk, as Paul would say. You're still at the point of sin/forgiveness/salvation, and have not yet begun to walk with Jesus.
Walk with Jesus. Be meek and humble, because He is meek and humble. Talk to Him, read about Him, immerse yourself in Him, and rebuke the devil when he accuses you of being a sinner.
You used to be a sinner. Now you're redeemed. Now you are brother, and joint heir, with Jesus.
Do what Jesus says. Abide in Him. And you will see your accuser slink away, as all of your sins were covered by the blood of Christ.
You'll never get all of the sin out of your life until Jesus finishes you in heaven. Look forward to that day.
