I feel Liam really answered this, however I would like to show some of the foundational concepts that help support his answer.
As Liam points out there are the two systems the "Faith Based System" and the "Law of Moses". These two systems are explained in Galatians under the terms Spirit and Flesh. Paul starts by explaining about trusting in the Circumcision.
Stand fast therefore in the liberty by which Christ has made us free, and do not be entangled again with a yoke of bondage. 2 Indeed I, Paul, say to you that if you become circumcised, Christ will profit you nothing. 3 And I testify again to every man who becomes circumcised that he is a debtor to keep the whole law. 4 You have become estranged from Christ, you who attempt to be justified by law; you have fallen from grace. 5 For we through the Spirit eagerly wait for the hope of righteousness by faith. 6 For in Christ Jesus neither circumcision nor uncircumcision avails anything, but faith working through love. (Galatians 5:1-6 NKJV)
So to restate: Jesus made us free from the "Works of the Law". So now we should no longer "Work the Law" becoming entangled to the yoke of bondage. Feeling the need to be Circumcised is putting our trust in a system that we have been freed from. Those that choose to follow the law are then required to keep the law because they have fallen from grace, by denying Christ. Instead we should eagerly wait for the hope of righteousness that comes from the "Faith Based System".
7 You ran well. Who hindered you from obeying the truth? 8 This persuasion does not come from Him who calls you. 9 A little leaven leavens the whole lump. 10 I have confidence in you, in the Lord, that you will have no other mind; but he who troubles you shall bear his judgment, whoever he is.
11 And I, brethren, if I still preach circumcision, why do I still suffer persecution? Then the offense of the cross has ceased. 12 I could wish that those who trouble you would even cut themselves off!
13 For you, brethren, have been called to liberty; only do not use liberty as an opportunity for the flesh, but through love serve one another. 14 For all the law is fulfilled in one word, even in this: “You shall love your neighbor as yourself.” 15 But if you bite and devour one another, beware lest you be consumed by one another! (Galatians 5:7-15 NKJV)
So to restate: The Galatians started off well, but this persuasion to follow the law does not come from Christ. "A little leaven leavens the whole lump." Even just a little bit of following the law can cause all to stumble. Whoever is convincing you to do this will bear his judgement. And if Paul was teaching "Works of the Law" why was he receiving persecutions? So Paul even wished those pushing this "Following of the Law" would emasculate themselves. Then gives a warning that our liberty should not be used as an opportunity for our bodies to perpetuate the Law.
I say then: Walk in the Spirit, and you shall not fulfill the lust of the flesh. (Galatians 5:16 NKJV)
So to restate: Trust in the "Faith" and you will not fulfill the "Works of the Law"
For the flesh lusts against the Spirit, and the Spirit against the flesh; and these are contrary to one another, so that you do not do the things that you wish. (Galatians 5:17 NKJV)
So to restate: The "Works of the Law" are against "Faith" and "Faith" is against the "Works of the Law"; and these are contrary to one another, so that you do not do the things that you wish.
But if you are led by the Spirit, you are not under the law. (Galatians 5:18 NKJV)
So to restate: But if you are in the "Faith", you do not do "Works of the Law".
Now the works of the flesh are evident, which are: adultery, fornication, uncleanness, lewdness, 20 idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, 21 envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God. (Galatians 5:19-21 NKJV)
So to restate: The result of "Working the Law" is adultery, fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God.
But the fruit of the Spirit is love, joy, peace, longsuffering, kindness, goodness, faithfulness, 23 gentleness, self-control. Against such there is no law. (Galatians 5:22-23 NKJV)
So to restate: But the result of "Faith" is love, joy, peace, longsuffering, kindness, goodness, faithfulness, gentleness, self-control. Against such there is no law.
And those who are Christ’s have crucified the flesh with its passions and desires. 25 If we live in the Spirit, let us also walk in the Spirit. 26 Let us not become conceited, provoking one another, envying one another. (Galatians 5:24-26 NKJV)
So to restate: nd those who are Christ’s have crucified the "Works of the Law" with its passions and desires. If we live by "Faith", let us also "Walk by Faith". Let us not become conceited, provoking one another, envying one another.
Brethren, if a man is overtaken in any trespass, you who are spiritual restore such a one in a spirit of gentleness, considering yourself lest you also be tempted. 2 Bear one another’s burdens, and so fulfill the law of Christ. 3 For if anyone thinks himself to be something, when he is nothing, he deceives himself. 4 But let each one examine his own work, and then he will have rejoicing in himself alone, and not in another. 5 For each one shall bear his own load. (Galatians 6:1-5 NKJV)
So to restate: If one who "Walks by Faith" is overtaken in any trespass (feels the need to use the Law to come to peace), you who are spiritual restore such a one in a spirit of gentleness, carefully considering the the situation lest you also be tempted to "Use the Law". Bear one another’s burdens, and so fulfill the law of Christ "The Faith". 3 For if anyone thinks himself to be something(as such a man who can escape fulfilling the Law without consequence), when he is nothing, he deceives himself. 4 But let each one examine his own work, and then he will have rejoicing in himself alone, and not in another. 5 For each one shall bear his own load.