Grace is the single thing that separates Christianity from man made religion. I’ve understood this a long time but it is because I was introduced to Christianity a long time ago and Lewis’ teaching not long after that.
Christianity doesn’t make sense to the natural man.
Paul says in Colossians 2 that the law is useless in restraining human passions. John says in 1 John that saying we don’t sin shows us to be liars.
Grace, therefore, must be about a different way of being righteous that has nothing to do with me. It’s a righteousness that’s given to me as a gift. That must mean that I continually get it without deserving it. In fact, it means that I continually am granted grace even though my behavior is continually saying I don’t deserve it.