Note: I have read the OP, but not the above discussion. I find I agree with 98% of what circuitrider and RomansFiveEight say and that we just tend to use different illustrations to make basically the same points. So my apologies if I end up repeating their thoughts, but I was already thinking about this yesterday and find your question a good exuce to put my thoughts down at this time.
Simply put, we either believe God is faithful and trustworthy or he is not. If he is, when you give your life over to him, it is preserved. He will not let you go and slip away from him. But, what God does in salvation is to restore the broken relationship that we have with him. He takes away our sin and casts them away, but he never casts us away.
But, can we pursue sin? Most certainly. We can, and sometimes we do pursue sin. What then?
I want to suggest that it depends on where your heart and your vision is. Those who have grown in Christ, who have become more sanctified, more Christ-like, are going to find that they sin less and less as they mature in him. By using this phrase "more Christ-like" it implies a sort of continum in which there would also be people who would be "less Christ-like." But, our salvation is not based on our merit, rather it is through the work of Christ. His grace is sufficient no matter how Christ-like or unChrist-like we are. Those who have place their hope in Christ keep him as the focus of our life, even if we should stumble and sin in the process. Our walk is a faith walk, trusting in Christ for our salvation while we seek to conform to his image as much as is possible, all the while knowing that the Spirit is working in us to accomplish that transforming process as well.
So, whether we become entirely sanctified or not, we still keep our focus our goal on Christ. And he remains the source of our salvation, however good or poor one is at bearing the image of Christ in the world. Such a person has nothing to worry about, they are secure in the work of Christ.
But, what if someone simply didn't want to be like Christ? What if they decided that they wanted to reach God based on their own power? What if they weren't interested in living in a relationship with God at all? Is that choice available to them? And the answer is that of course it is. God never takes a person's free will away from us.
Notice in John 17 how Jesus speaks of how the Father gave all of his disciple to him. ALL of them. Not all except Judas, but all of them. And yet, he lost Judas. Why? Not because of some failing on Jesus' part, but because Judas made a different choice with his life. And God allows us to make those choices.
Now, some people erroneously believe that once one gives their life over to God, that we lose our free will to turn away from God. That simply isn't true. But, rather than argue philosophy, let me let the scriptures speak to that issue:
Hebrews 6:4-6
It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age and who have fallen away, to be brought back to repentance. To their loss they are crucifying the Son of God all over again and subjecting him to public disgrace.
Here we have a passage that identifies there being a group of people who were not only "enlightened," but had actually "tasted the heavenly gift, who have shared in the Holy Spirit."
Now, throughout Hebrews the gift that comes from God is the gift of salvation, so I would suggest to you that this means these people were saved. Yet, the text goes on to say that they have "fallen away." Indeed, so complete is this that they cannot repent again. So, right in the scriptures we have an example of people who were once saved (at least according to the author of Hebrews they were saved), but don't remained saved (again if we are to believe Hebrews). Those who teach "Once Saved Always Saved" would be more aligned with scriptures if they were to teach "Once Saved, No Playing YOYO with your Salvation."
But, even here this story is not told to fill us with fear. For, "even though we speak like this, dear friends, we are convinced of better things in your case—the things that have to do with salvation. God is not unjust; he will not forget your work and the love you have shown him as you have helped his people and continue to help them" (Hebrews 6:9-10). Just "continue" to keep your focus where it belongs, not on your ability, but God's ability. He is the one who saves you. Even if you are not good at the Christian walk, "imitate those who through faith and patience inherit what has been promised"(Hebrews 6:12) and you can be certain that God will keep you secure. You would have to choose to actively turn your back on God, only then would salvation be at risk.
