Verse 1 of this chapter says this: "It was for freedom that Christ set us free; therefore keep standing firm and do not be subject again to a yoke of slavery." Too often, I've heard this verse used as a principle against slavery to sin (like immoral living and bad habits). However, in the context of chapters 4 and 5, Paul is talking about the slavery involved in living according to the law or trying to earn favor through good works.
So the focus is on people who try to be good for self-centered reasons, possibly to feel better about themselves or to earn a godly reputation. It's not about people choosing to do evil things. I feel the latter "slavery" would be easier to identify and address, for when someone seems to have things lined up and appears blameless, they may feel themselves above correction or even exhortation. These people may be heavily involved in the church and/or ministry and be viewed as examples in the body of Christ...because they are good and do good things.
But God doesn't call us to a "good" life. We cannot follow a list of rules and expect to qualify as a successful Christian. In fact, in a later epistle, Paul says, "the letter kills, but the Spirit gives life" (2 Cor. 3:6b). To have that outward righteousness without the cleansing and filling of the Spirit is to be Pharisaical, the "whitewashed tombs" of Matthew 23:27.
Galatians 5:4-6 says, "You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace. For we through the Spirit, by faith, are waiting for the hope of righteousness. For in Christ Jesus neither circumcision nor uncircumcision means anything, but faith working through love."
As a teenager, I thought that living by the Spirit would be much easier than living by the law. I read verse 18 ("But if you are led by the Spirit, you are not under the Law") as gleeful liberation from strict standards and regulations that I had trouble pinpointing to Biblical principles. However, now I understand that the law is the easier choice because it is within our grasp. It's easier to perform expectations that are affirmed by other believers--this can be done on self-reliance. It's much harder to surrender myself to the Spirit, always pressing for a closer relationship and a purity that will only be realized when I see Christ. It's much harder to seek the Lord in the quiet than to rave about how I am being used by Him in the crowds. In other words, if there is no "quiet," there should be no "crowds."
Living by the Spirit also means opening up myself for His correction. His holiness should pierce the pride and lust that no one else sees. His love should build me up where no one else saw brokenness. And the fruit of the Spirit (vs. 22-23) is the result of such purging and guidance by the Spirit--not by added effort on my part to be "good."
One last note on this chapter: He who lives by the Holy Spirit is truly humble. Verse 26 says, "Let us not become boastful, challenging one another, envying one another." Those who bear the "yoke of slavery" see themselves in competition with other believers, whether overtly or subconsciously. They desire to be better Christians, to demonstrate how good they are, and to cause others to look up to them and want to be like them. On the contrary, someone who walks by the Spirit understands his dependence on God and role in the church--and chooses not to draw attention to himself.
The way of the law is very tempting, as it feeds our pride. But with it comes that heavy yoke--chaining us to our peers and stealing the glory that should be God's alone.
