When you accept who God says you are and claim what He has done for your salvation, your human nature is declared dead. Your human nature is corrupt, and God did not send Jesus to fix it. This nature is meant to die. Your human nature becomes crucified (Romans 6:6), and you are given an entirely new nature through the Holy Spirit (2 Corinthians 5:17).
However, this gives you a dual nature. Even though one nature is technically dead to you, both natures will fight with each other, pulling you in two different directions because they are diametrically opposed. Paul talks about this in Romans 7:15-25. Whichever nature wins is the one you “feed,” so to speak. You get to decide which one wins, and sometimes it’s very difficult since you are practically fighting with yourself. Since your old nature is supposed to be dead, you should reckon yourself dead to that sin nature (Romans 6:11). But you can’t win this battle without the God who gave you your second nature.
Don’t go carrying around or returning to a rotting, dead body. God made you for better, that’s why He gave you a whole new nature instead of leaving you with the old one.