Fallen from grace does not mean "living in sin" as we have been religiously taught or that we hear from the world's media. So and so was caught stealing $100,000,000 from his hedge fund - "he has fallen from grace".
To fall from grace as Paul used the term is to rely on our own works for righteousness - such as "doing good works to remain saved".
The Judaizers in Paul's day came to the Galatians and said "You must be circumcised" once you are in Christ now. It is the "doing of the law in order to achieve and maintain righteousness."
This actually goes back before the Mosaic Covenant to Abraham as a "sign of you are in the covenant now" and God said if they weren't circumcised - they were not in the covenant - so you can understand how Christians could fall for this.
Galatians 5:3-4 (NASB)
[SUP]3 [/SUP] And I testify again to every man who receives circumcision, that he is under obligation to keep the whole Law.
(Justified by law means - you are justifying or making yourself righteous "by what you do or don't do". The whole law of Moses was based on this.)
[SUP]4 [/SUP] You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.
The Greek word for "severed" means "to make idle" or "useless" "to nullify".
This is why those that say we need to do good works in order to stay saved are really nullifying or making useless or idle the grace of God from operating in our lives like it was meant to.
2643. [FONT="Galatia Sil" !important]καταργέω[/FONT] [FONT="Gentium" !important]katargeō[/FONT] verb
Make idle or useless, waste, abolish, cease, do away with, destroy.
[FONT="Gentium" !important]Katargeō[/FONT] means “to abolish” or “to nullify.” In classical Greek [FONT="Gentium" !important]katargeō[/FONT] means “to render inactive, to put out of use, to cancel, bring to nothing” or “do away with.”
Complete Biblical Library Greek-English Dictionary, The - The Complete Biblical Library Greek-English Dictionary – Zeta-Kappa.