For anyone that may read this, it's 4 pages long.  It was written to someone I was having a discussion with, and I'm basically posting here, just to save it, and have it to reference in the future.  The first part are verses that talk about us already being forgiven, as opposed to the verse that says God won't forgive you unless you forgive others.  I believe that verse applied prior to the cross, and these verses apply after the cross.  The rest is an overview of the book of Galatians and what "Falling from grace" means in context with the rest of the book.  

Verses that talk about already being forgiven:

Ephesians 4:32 “Be kind to each other, tenderhearted, forgiving one another, just as God through Christ has forgiven you.”  (I already gave you this verse)

Colossians 3:13 “Make allowance for each other’s faults, and forgive anyone who offends you. Remember, the Lord forgave you, so you must forgive others.”

Ephesians 1:7 “He is so rich in kindness and grace that he purchased our freedom with the blood of his Son and forgave our sins.”

A bit of context for the verse in Galatians chapter 5 that talks about falling from grace:

The whole book of Galatians is about Paul being commissioned to preach the Gospel among the Gentiles or non-Israelite people, and others were coming in and telling the Gentile people that the Gospel alone was not enough and they had to go back and follow the Mosaic Law in order to be saved.  Paul got very angry about it, and basically said by believing that they had to mix the law with grace, they were morons.  In the Bible it uses the word, “foolish,” but in modern day times people say the word, “moron” would be closer to what Paul was saying.  Here is an overview of the book of Galatians:

Galatians 1:6-7 “I am astonished that you are so quickly deserting the one who called you to live in the grace of Christ and are turning to a different gospel— ⁷ which is really no gospel at all. Evidently some people are throwing you into confusion and are trying to pervert the gospel of Christ.”

Galatians 1:11-12 “I want you to know, brothers and sisters, that the gospel I preached is not of human origin. ¹² I did not receive it from any man, nor was I taught it; rather, I received it by revelation from Jesus Christ.”

Galatians 2:2 “I went [to preach to the Gentiles] in response to a revelation and, meeting privately with those esteemed as leaders, I presented to them the gospel that I preach among the Gentiles. I wanted to be sure I was not running and had not been running my race in vain.” 

(In context this talking about consulting with Israelite/Jewish leaders to make sure they were all on the same page, and that they were in agreement with what Paul was doing. And I added the brackets above for context.)

Galatians 2:7 “they recognized that I had been entrusted with the task of preaching the gospel to the uncircumcised,^[ just as Peter had been to the circumcised.”

Note here: Circumcision represented a covenant.  Israelites in the Old Testament were commanded to be circumcised, and that sealed their Covenant with God, and non-Israelites (or non-Jews) did not practice circumcision.  So this statement is talking about Paul preaching the Gospel to non-Israelite people.  Or the uncircumcised.  But it is also important to know that circumcision for covenant purposes, was done away with after the cross. Paul talks about it later in the book that circumcision no longer profits you anything in God’s eyes. 

Galatians 3:1-9 “Oh, foolish Galatians! Who has cast an evil spell on you? For the meaning of Jesus Christ’s death was made as clear to you as if you had seen a picture of his death on the cross. ² Let me ask you this one question: Did you receive the Holy Spirit by obeying the law of Moses? Of course not! You received the Spirit because you believed the message you heard about Christ. ³ How foolish can you be? After starting your new lives in the Spirit, why are you now trying to become perfect by your own human effort? ⁴ Have you experienced so much for nothing? Surely it was not in vain, was it?

⁵ I ask you again, does God give you the Holy Spirit and work miracles among you because you obey the law? Of course not! It is because you believe the message you heard about Christ.

⁶ In the same way, “Abraham believed God, and God counted him as righteous because of his faith.” ⁷ The real children of Abraham, then, are those who put their faith in God.

⁸ What’s more, the Scriptures looked forward to this time when God would make the Gentiles right in his sight because of their faith. God proclaimed this good news to Abraham long ago when he said, “All nations will be blessed through you.” ⁹ So all who put their faith in Christ share the same blessing Abraham received because of his faith.”

Galatians 4:8-12 “Before you Gentiles knew God, you were slaves to so-called gods that do not even exist. ⁹ So now that you know God (or should I say, now that God knows you), why do you want to go back again and become slaves once more to the weak and useless spiritual principles of this world? ¹⁰ You are trying to earn favor with God by observing certain days or months or seasons or years. ¹¹ I fear for you. Perhaps all my hard work with you was for nothing. ¹² Dear brothers and sisters,^[f] I plead with you to live as I do in freedom from these things, for I have become like you Gentiles—free from those laws.

Note: Verse 10 is talking about the Mosaic Laws the Israelites had.  I copied this from the internet: “Paul now points to some specific works of the law that these Galatian Christians have begun to follow. They have started to observe specific "days and months and seasons and years." He means that they have started to observe and celebrate all the special days and holidays Israel was commanded to observe under the law of Moses.” (From Bibleref.com)

Galatians 5:1-16 “So Christ has truly set us free. Now make sure that you stay free, and don’t get tied up again in slavery to the law. ² Listen! I, Paul, tell you this: If you are counting on circumcision to make you right with God, then Christ will be of no benefit to you. ³ I’ll say it again. If you are trying to find favor with God by being circumcised, you must obey every regulation in the whole law of Moses. ⁴ For if you are trying to make yourselves right with God by keeping the law, you have been cut off from Christ! You have fallen away from God’s grace.

(This is the verse we are discussing)

⁵ But we who live by the Spirit eagerly wait to receive by faith the righteousness God has promised to us. ⁶ For when we place our faith in Christ Jesus, there is no benefit in being circumcised or being uncircumcised. What is important is faith expressing itself in love.

⁷ You were running the race so well. Who has held you back from following the truth? ⁸ It certainly isn’t God, for he is the one who called you to freedom. ⁹ This false teaching is like a little yeast that spreads through the whole batch of dough! ¹⁰ I am trusting the Lord to keep you from believing false teachings. God will judge that person, whoever he is, who has been confusing you.

¹¹ Dear brothers and sisters^, if I were still preaching that you must be circumcised—as some say I do—why am I still being persecuted? If I were no longer preaching salvation through the cross of Christ, no one would be offended. ¹² I just wish that those troublemakers who want to mutilate you by circumcision would mutilate themselves.

¹³ For you have been called to live in freedom, my brothers and sisters. But don’t use your freedom to satisfy your sinful nature. Instead, use your freedom to serve one another in love. ¹⁴ For the whole law can be summed up in this one command: “Love your neighbor as yourself.” ¹⁵ But if you are always biting and devouring one another, watch out! Beware of destroying one another

¹⁶ So I say, let the Holy Spirit guide your lives. Then you won’t be doing what your sinful nature craves.”  

(I take this to mean that instead of being guided by the law, be guided by the Holy Spirit instead)

Galatians 6:12-13 “Those who are trying to force you to be circumcised want to look good to others. They don’t want to be persecuted for teaching that the cross of Christ alone can save. ¹³ And even those who advocate circumcision don’t keep the whole law themselves. They only want you to be circumcised so they can boast about it and claim you as their disciples.”

Anyway, I just wanted to give you some context the verse highlighted in yellow (Galatians 5:4)

 Paul spent the whole book trying to tell the Galatian people that they were foolish for believing that they still had to follow the Mosaic Law in order to achieve salvation or any of God’s blessings.  The Gospel message is grace through faith alone, not grace plus works.  People were coming in and perverting the Gospel, and mixing grace with the law. 

So anyway, I agree with Lawson that falling from grace is not talking about committing some grievous sin, nor is talking about losing your salvation.  I believe Paul was saying that instead of reaping the benefits of grace they were trying to go back to the Mosaic Law to be justified in God’s eyes, and the only way we can be justified is through faith in Jesus. 

We can’t earn our salvation, or healing, or any of God’s promises.  We receive them by faith and not through works.  Paul was saying in chapter 5, verse 3 that if we want to be justified through works, then circumcision isn’t the only law they would have to obey, they would have to follow all of the 613 laws given through Moses, and be perfect.  No one can do that, and that’s precisely why we need a Savior. 

But anyway, this is long and drawn out, but I do believe that falling from grace means that we are not reaping the benefits of grace, because we are trying to earn them by works, instead of receiving them through faith.  And that is what Lawson said.