Our God is a holy God. He is a righteous God. He created us unto righteousness. We fell out of His standard and sin became our new way of life. Originally, we were to be holy and righteous as He is holy.
The nature of sin wasn't God's original nature which He created us. He created us in His image and we know that His image is holiness and righteousness. The devil planted the seed of sin in us. He made us turn against the commandments of God.
That has been our nature since then. We are rebellious and disobedient to the commandments of God. We delight in sinning. Our flesh and the world works against the commandments of God. So, to do good becomes difficult.
The ability to do what is good is not in us. Our flesh and the devil works against the will of God. We cannot on our own do what is good. We need the help of God. This is the cry for salvation.