The reason why you keep asking God to forgive the same sins over and over again is because you aren't really sure if He has actually forgiven them. If you knew beyond doubt that He had forgiven them, then there wouldn't be any reason to keep on confessing them, would there?
And you can have this assurance! God's forgiveness of our sins isn't based on an impulse or a whim. It is based solely on one fact: Jesus Christ died for our sins. You see, when Jesus Christ died on the cross, He became the final and complete sacrifice for our sins. All our sins were placed on Him, and He took upon Himself the judgment we deserved. The Bible says, "Christ died for sins once for all, the righteous for the unrighteous, to bring you to God" (1 Peter 3:18).
Let me put it another way: Jesus Christ paid your debt—the debt you owed God because of your sins. He didn't pay just part of it; He paid it all! And when we come by faith to Him and receive Him into our hearts, He takes away all our sins—not part of them, but all of them. The Bible says, "God made you alive with Christ. He forgave us all our sins" (Colossians 2:13).
Why did He do this? He did it because He loves you, and He wants you to be with Him in Heaven forever. Respond to His love today, by asking Christ to come into your life and cleanse you of every sin you have ever committed—and He will.