6 Therefore as you have received Christ Jesus the Lord, so walk in Him, 7 having been firmly rooted and now being built up in Him and established in your faith, just as you were instructed, and overflowing with gratitude.
Col 2:6-7 (NASB)6 And now, just as you accepted Christ Jesus as your Lord, you must continue to follow him.7 Let your roots grow down into him, and let your lives be built on him. Then your faith will grow strong in the truth you were taught, and you will overflow with thankfulness.
Col 2:6-7 (NLT)
These verses are part of Paul's reminder to the church at Colosse that they are to follow Christ with their lives. Then, as now, there was a culture pressure to put your faith into a box, and take it out only when you wanted to. The Roman world, at the time of this writing, offered no persecution to believers in Christ, affording them the same liberties they gave the Jews. There were frequent outbursts between Jews and Christians, but a Gentile city like Colosse didn't deal with those problems for long.
Instead, the pressure on Christians was to allow the world to shape their faith. There would have been cultural pressure to participate in the various pagan entertainments, business pressure to pursue greedy deals, religious pressure to accept all of the other beliefs as equally valid.
Paul is instructing the Church not to treat their faith as something that happened, and that they can then go about life as they wished. They are to grow, now that they are rooted in Christ. Think of the trees you can buy at Wal-mart every spring. They are small, and will not grow much bigger because they have shallow roots. Or consider Christmas trees, that you can buy a 'live' tree, but if you take it home and stick it in the yard, it will not grow. It has no life possibilities because it has no root. Christians have the possibility of growth because they are rooted in Christ.
The Colossians needed to understand that this affected every aspect of their life. Part of the difficulty was that, in avoidance of legalism, there was a tendency to say that Christian life had no rules. Paul wanted them to understand that true Believers will live out their salvation in their behaviors, thoughts, actions, and speech.
Sometimes believers don't follow through, but that does not take away God's grace in their lives. Eventually, the Holy Spirit will convict them and draw them back, or they will so harden themselves against God that they don't hear Him. We have to remember that God is in the process of making us fit for eternity, and when we cross from this side to that one, we will see how far we've come as well as how far we have left to go.