In Galatians chapter 4 Paul was telling us about the differences between the two covenants.  Let's just look at verse 24-26 (Galatians 4:24-26) [NLT] "These two woman serve as an illustration of God's TWO covenants. The first woman, Hagar, represents Mount Sinai in Arabia, because she and her children live in slavery to the law.  (26) But the other woman Sarah, represents the heavenly Jerusalem. She is the free woman, and she is OUR mother."

So Hagar represents the Old Covenant Law that was given on Mount Sinai, and Sarah represents the New Covenant of Grace.   Verse 31 of chapter 4 says, "So, dear brothers and sisters, we are not children of the slave woman, we are children of the free woman."

So the two woman represented the two covenants, and OUR Covenant is represented by Sarah.  Let's back up earlier in the Book of Galatians to chapter 3:23-29 "BEFORE the way of faith in Christ was available to us, we were placed under the guard of the law.  We were kept in protective custody, so to speak, UNTIL the way of fiath was revealed. (24) Let me put in another way.  The law WAS our guardian UNTIL we could be made right with God through FAITH.  (25) And NOW that the way of faith has come, we no longer need the law as our guardian.  (26) For you are all the children of God through FAITH in Christ Jesus.  (27) And all who have been united with Christ in baptism have put on Christ, like putting on new clothes.  (28) There is no longer Jew or Gentile, slave or free, male of female.  For you are all one in Christ Jesus.  (29) And now you belong to Christ, you are the true children of Abraham.  You are heirs, and God's promise to Abraham belongs to you."

I want to look at verse 29 in the KJV, "And if ye be Christ's, the ye are Abraham's seed, and heirs according to the promise."

So now we have some back story before we get into reading chapter 5.  Anyone that is in Christ, is considered to be Abraham's seed, and therefore a child of Sarah which represents the New Covenant.  The law was only intended to be until Christ Came, and we could be made right with God through FAITH in Jesus, and not through keeping the Mosaic Law.  Now let's read the verse 1-6 of chapter 5:

(1) So Christ has truly set you free.  Now make sure you stay free, and don't get tied up again slavery to the law.  (2) Listen! I Paul, tell you this: if you are counting on the circumcision to make you right with God, then Christ will be of now effect to you.  (3) I'll say it again, if you are trying to find favor with God by being circumcised, you must obey regulation in the whole law of Moses.  (4) For if you are trying to make yourself right with God by keeping the law, you have been cut off from Christ! You have fallen away from God's grace. (5) But we who live by the Spirit eagerly wait to receive BY FAITH the 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."  

So as Joseph Prince said in a previous post, our blessings from God come from our faith in Jesus, and not in our own self efforts and trying to keep the Mosaic Law.  We are no longer under that law, we are now under grace, and going back to the law and trying to earn God's blessings through self effort, is what falling from grace means. 

Does that mean we are free to sin if we are not governed by the Law of Moses?  Of course not.  Paul goes on to say in Galatians 5:13-16 "For you have benn 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.  (14) For the whole law can be summed up in this ONE command, 'Love your neighbor as yourself.'  ....(16) So I say, let the Holy Spirit guide your lives.  Then you won't be doing what your sinful nature craves."  

Being led by the Holy Spirit is far supior to being guided by the Mosaic Law.  The law only told us what NOT to do:  Don't commit adultery, don't steal, don't lie, etc.  But the Holy Spirit teaches us how to love our spouse and have a good relation ship. The Holy Spirit will teach us to give generously to those in need, and the Holy Spirit will teach us to edify others and lift them up in love.  Being led and guided by Him goes far beyond not doing things wrong, and teaches to love our neighbors as ourselves.

Galatians 5:18 "But when you are directed by the Spirit, you are not under the obligation to the law of Moses." 

Romans 7:4 "So my dear brothers and sister's this is the point: You died to the power of the law when you died with Christ.  And now you are united with the one who was raised from the dead.  As a result you can produce a harvest of good deeds for God.   Verse 6 "But now we have been released from the law, for we died to it and are no longer captive to it's power.  We can now serve God not in the old way of obeying the letter of the law, but in the new way of living in the Spirit." 

Anyway, I firmly believe that falling from grace means going back to the Mosaic Law to earn God's favor and blessing, rather than putting our faith in Jesus and receiving right standing with God through through believing in His finished work.