I have some thoughts from Galatians to share. I'm wondering whether they are accurate? (It's also possible that they're very obvious to everyone except me, but to me these are new and exciting thoughts). Sorry, it's long. I am too verbose to make a good blogger!
Firstly, what is the problem in Galatia? Obviously false teaching. But there must have been something in that teaching to make it attractive to the Christians. Although they were doubtless "foolish" (3:1) to go along with the false teachers, they surely didn't think that they were "deserting him who called you in the grace of Christ" to turn to "a different gospel" (1:6). They must have thought they were being offered something good. I would suggest that what they wanted was to be righteous - surely a good desire! The false teachers offered them a way to be righteous, namely, by the observance of the law: the law that was given by God.
Now, Paul had himself once relied on the law for righteousness. He was, after all, a Jew by birth, and not a Gentile sinner (3:15). But he had come to see that works of the law do not give righteousness - only faith in Christ does (3:16). That also led to another realisation: whereas he had thought that he, with his law-keeping, was different to all the "Gentile sinners", he now testified that "we too (i.e. the Jews) were found to be sinners" (3:17). He was in the same boat as the Gentiles he had once despised!
Paul is therefore forced to put his faith solely in Christ, and as he does so he can testify that the old man he used to be, with both his sin and his law-keeping, died - "crucified with Christ" (3:20). The life he now lives is not his own - it is Christ who lives in him, and he lives solely by faith in Christ (3:20).
The Galatians have had a similar experience. In Paul's preaching, Christ was portrayed as crucified before their eyes (3:1). They heard, and responded with faith, and God gave them his Spirit (3:2). Indeed, as they continue to hear and believe, God continues to supply the Spirit (3:5). We can assume that Paul's faith that he was crucified with Christ and that his old self no longer lives is also the faith of the Galatian Christians.
After a few arguments about the uselessness of the law to justify (3:10-14) and its obsolescence with the coming of Christ (3:15-4:7), Paul expresses exasperation that the Galatians are turning to the law - which he directly equates with a return to their old pagan religion! (4:8-11). This would be to return to slavery. Christ did not set them free from paganism in order to enslave them to the law; rather, "for freedom Christ has set us free" (5:1). In fact, rather than seeking righteousness through the law, Paul is now through the Spirit and by faith eagerly awaiting "the hope of righteousness" (5:5), a hope given him in Christ (5:6).
Now, I imagine the Galatians saying this: 'but Paul, all you are offering us is the righteousness of Christ (which is in heaven) and the hope of righteousness (which is reserved for the resurrection). Sure, we can possess the former by faith and look forward to the latter, but what about now? The law gives us some righteousness that is tangible, something we can experience. You just seem to offer pie in the sky in comparison'.
And Paul says no. The Christian life now is to be characterised by increasing righteousness in behaviour, but it is not to be brought about by the law but by walking by the Spirit (5:16). If the Galatian Christians walk by the Spirit, the Spirit makes war on the evil desires of their flesh (5:17). It's not their fight, but his. And how do they receive the Spirit? By hearing the gospel of Christ crucified and believing it (3:2-5). The conclusion is that nothing counts except the fact that Christ was crucfied, and in him I was also crucified, my old self being killed to make way for a new creation (6:14-15). And this I know only by faith (hence the parallel between 5:6 and 6:15).
What does this mean for us? It means we must live by faith. Christ was crucified, objectively, in space and time, in history. In him, I was crucified and killed - the old me, the one enslaved to sin, is dead. Now, Christ lives in me in all his perfect righteousness. But I do not see that in my experience. If I look at myself, I see sin, not righteousness. So the temptation will be to pursue an experience of righteousness - whether through rules, or accountability, or mysticism (the latter - an attempt at mystical righteousness - appears to be the problem in Colossae. Paul points them to the righteousness of Christ in heaven [Col 3:2]). I want to be able to look at myself and see some righteousness. But that is not faith. Faith is believing what I do not see. Faith is trusting in Christ's righteousness, and waiting patiently for the day when I will be made perfectly righteous in my experience. And actually, as I believe what the gospel says about me - that my sinful self died with Christ and I am now raised to new life - the Holy Spirit begins to make it true in my experience.
So my fight is not the fight against this sin or that sin, or the fight to be more godly in this or that area of life. Not primarily anyway. My fight is to believe, trust and live by the finished work of Christ, looking not to myself but to him. God give me grace to do so.