"The minute we think that anybody owes us grace, a bell should go off in our heads to alert us that we are no longer thinking about grace, because grace, by definition, is something we don’t deserve. It is something we cannot possibly deserve. We have no merit before God, only demerit. If God should ever, ever treat us justly outside of Christ, we would perish. Our feet would surely slip."
Read the full illustration of this principle by RC Sproul here