Colossians 1:21-23 ESV –
 And you, who once were alienated and hostile in mind, doing evil deeds,  he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him,  if indeed you continue in the faith, stable and steadfast, not shifting from the hope of the gospel that you heard, which has been proclaimed in all creation under heaven, and of which I, Paul, became a minister.
The Alienated and the Reconciled
Here there are two types of people represented in the Colossians: the old, and the new. In verse 21 Paul says that the Colossians were once “alienated and hostile in mind, doing evil deeds” they had since been reconciled with GOD through Christ. This is important to consider. There is no middle-ground alternative. One is either with GOD or alienated from him, in the latter case the devil is at work in him (see also Ephesians 2:1-2).
The alienated: What makes one alienated from GOD?
I think that an important phrase to consider from verse 21 when answering this question is ” hostile in mind.” Compare this with Romans 8:7.
Romans 8:7 ESV –  For the mind that is set on the flesh is hostile to God, for it does not submit to God’s law; indeed, it cannot.
The mind set on ungodly things brings hostility between GOD and man. This hostile mind leads to evil, for the hostile mind is unable to submit to GOD’s law.
The reconciled: What is the reconciliatory force between GOD and man? Who initiates this force?
Since the mind that is apart from GOD sets itself on things of this world and can not submit to GOD’s law, GOD must grace us with a changed mind, one that turns to seek him, one that is set on godly things, and in that grace we are able to come to him through Christ and be reconciled.
Ephesians 2:8-9 ESV –  For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,  not a result of works, so that no one may boast.
Colossians 1:22 ESV –  he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him,
GOD changes our minds and hearts so that we are able to come to him in obedience, through faith, and accept his gift of reconciliation. I find it important to point out that the work of a changed mind and of salvation through faith is GOD’s doing, and not ours by works, in order to explain the words of Colossians 1:23.
Proof of Reconciliation
Colossians 1:22-23 ESV –  he has now reconciled in his body of flesh by his death, in order to present you holy and blameless and above reproach before him,  if indeed you continue in the faith, stable and steadfast, not shifting from the hope of the gospel that you heard…
Verse 23 is not pointing out the means by which one is saved, but evidence of one’s salvation. Verse 22 is the means in which verse 23a comes to fruition. Which is to say that because Christ has reconciled us to him through faith, we will remain steadfast in him. Verse 23 is a confirmation of verse 22! I say this because:
1. Verse 22 says that we are reconciled and made blameless through the work of Christ. (Not our work)
2. The aforementioned Ephesians 2:8-9
3. This idea is echoed in Titus 1:15-16 which says:
Titus 1:15-16 ESV –  To the pure, all things are pure, but to the defiled and unbelieving, nothing is pure; but both their minds and their consciences are defiled.  They profess to know God, but they deny him by their works. They are detestable, disobedient, unfit for any good work.
In 1 John 2:19 the apostle John speaks about those who began in the faith but did not show themselves to be faithful:
1 John 2:19-20 ESV –  They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us.  But you have been anointed by the Holy One, and you all have knowledge.
So to review, Colossians 1:21-23 teaches us:
1. Those with their minds set on the world are alienated from GOD
2. God changes our minds to be set on seeking him by his grace, so that we can accept the reconciliation set forth by Christ in the redemptive work of his death and resurrection.
3. Our obedience and our steadfast abiding in the hope of the gospel, is proof of our salvation. It is not the means, but rather the result of GOD work in us. And it is GOD that gives us the ability to do this, because on our own we have minds hostile toward him that are incapable of obedience.
I would like to make clear that I am not proposing that we have no choice in the matter of our salvation, but rather, I am saying that the scriptures point out to us that GOD is the initiator in the relationship. GOD calls us to come to him in repentance and faith, as well as to be obedient to him. Fortunately he also supplies us with the means to do this by his wonderful grace, as we were unable to do so because of our hostile minds. This is a gift that he offers to all, for the scriptures say:
2 Peter 3:9 ESV –  The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance.