You are correct regarding repent vs. penance. CC teaches we must do penance, because that is how we complete what is lacking in Christ’s suffering.
Yes, one must turn their lives 180 degrees IF THEY HAD BEEN LIVING IN SIN!
What about somebody like me, who sins, but never led a life of Sin. How could I turn 180 degrees? I have always put my entire faith in God, I always tried not to sin, even as a teenager. I have always and presently evangelize myself. If I did a 180, I’d be on the wrong path!
To me, faith is a journey, not a one time experience. I don’t deny one can be “born again” in the Fundamentalist usage, but for many people like myself, I had small faith when I was small, and as I grew older, more faith became fuller. Does that make sense?