That depends on whether you believe in Eternal Security. I didn't at first but from studying that is what I now believe. You can lose your rewards but not your salvation. The only unpardonable sin is the sin of unbelief. Once you belong to God nobody has the power to snatch you away.
I generally try to avoid doctrinal arguments. They are secondary and deflect attention away from the basic Gospel of the death, burial, and resurrection of Jesus. Nobody is saved by religion and most impose extra man made rules. Nothing wrong with a lot of that if you are comfortable with it and it doesn't go against the core Gospel. The problem is when you rely on religion to save you instead of a relationship with God.