[wideawake]

There is no loop.

I think you are conflating sin itself with the capacity to commit sin.

When Christ forgives sin, it is forgiven, it is gone.

The forgiven individual still has the ability to commit sins. If the forgiven individual commits sin again after they've been forgiven, he must repent and ask for God's forgiveness.

[plain talk]

I suggest you study this further. I will do likewise.