Freedom in Christ comes from eliminating sin. You cut off the devil's stronghold upon you when you realized that Jesus was the way and accepted him as your Savior. Are you still striving because you haven't let it go and are still fretting over sin from the past?
As I began to pray my usual prayer this morning, I kept moving about restlessly. I decided that I needed to start over and pray again, only this time, I needed to sit still. I should preface this by saying that I wait to open the scriptures until I've prayed, so when I opened my Bible, I realized that the next chapter of Hebrews was about rest. Did you know that the rest spoken of in scripture is about resting from striving over sin? We all need rest from work, but you will never truly rest until the devil no longer imprisons you because of your sin. Stop letting the enemy accuse you! You have Jesus, who was sacrificed to pay the price for your sin; the devil can't get to you anymore. Let go of your guilt and shame! It's time to rest.
Therefore, while the promise of entering his rest still stands, let us fear lest any of you should seem to have failed to reach it. Hebrews 4:1