Therefore, as you received Christ Jesus the Lord, so walk in him, rooted and built up in him and established in the faith, just as you were taught, abounding in thanksgiving.
This is a wonderful passage to understand Christian growth and maturity. We received Christ as the Lord, we walk in him, are rooted and built up in Christ, and in that commitment we become established in our faith through the teaching of God's truth and the good news of the gospel message. This is the way each Christian is supposed to mature.
The New Testament is very clear that Christianity is a lifestyle. Christ changes us as we are in relationship with Him. Our acceptance of Him as Lord is more than just acknowledgement of historical fact. For instance, I can believe that John F. Kennedy existed as a historical person although I never met him. I can know he achieved many things. But it does not then follow that I order my life around that fact and find my life transformed by living "in Kennedy". It is completely different with Jesus. Our faith in Him becomes a living faith because He is God and alive in us. We gladly build our lives around that relationship of faith.
The way that Paul helps us understand that relationship in the book of Colossians is found in the theme of the book summed up in two simple yet enormously impacting words: "in Christ". The text of Colossians helps us understand what being in Christ means. This chart from the ESV Study Bible gives us a lot to look at:
1:14 IN WHOM we have redemption
1:16 IN HIM all things were created
1:19 IN HIM all the fulness of God was pleased to dwell
1:22 Reconciled IN HIS BODY of flesh
2:3 IN WHOM are hidden all the treasures of wisdom and knowledge
2:6 walk IN HIM
2:7 rooted and built up IN HIM
2:9 IN HIM all the fulness of deity dwells bodily
2:10 you have been filled IN HIM
2:11 you were circumcised IN HIM
2:12 IN HIM you were raised up
2:15 triumphing over them IN HIM
3:20 pleasing IN THE LORD
4:7 fellow servant IN THE LORD
4:17 the ministry that you received IN THE LORD
Analyzing the implications of being "in Christ" is one way of knowing what Christian growth looks like. And when we begin to walk that way, we will live more and more like Jesus in this world!