Not free to do nothing

I've been reflecting on Christian freedom lately, and I'm discouraged. Here's the party line as far as the Reformed are concerned. There is nothing that anybody can do to earn salvation. Salvation is a gift from God, imparted to those who have faith. You don't do anything to earn it, you merely receive it the way you might receive a present that someone was giving you. Faith is the instrument by which you receive this gift. Faith itself is a gift. You can not beleive of your own accord. The Holy Spirit must move in your heart to open your eyes to see the gift. The Holy Spirit gives you faith. By faith, you receive salvation.

Fine.

But, people want to know for sure whether or not they have salvation. Funny thing is, part of having faith means having assurance. In other words, faith that isn't assured isn't real faith. Now, is there no room for doubt. Yes. In fact, doubt can be healthy and keeps humble. But what is the difference between real faith that suffers from doubt, and unsaving false doubting faith? It's sort of like being in a castle that's under attack. True faith recognizes the attack, but is firmly lodged inside the castle, firmly aware that God is fighting the battle and that the castle will stand firm despite the attack. Doubting faith rests on no firm foundation and is ultimately unsure of its disposition.

I'm not sure how well the analogy works. But anyway, there's another way to have assurance. A good tree produces good fruit. A Christian's life will reflect the gratitude that comes from having received the gift of salvation. The Reformed creeds suggest that the fruit evident in my life is evidence of salvation working through me. OK, good.

Now, my problem is this. If salvation is a gift that is not dependent upon my works, am I free to do nothing once I've received the gift of salvation? If I'm counted righteous before God because of Christ's atoning sacrifice must I do works in order to maintain that status? Or, isn't it the case that a Christian will necessarilly produce good works because the outpouring of good works is a natural product of being a new creation filled with the Spirit? In other words, I'm afraid that even though my works do not earn my salvation, my works are necessary for my salvation, because if I don't do them, then I've no way of knowing the efficaciousness of my salvation.
Now, the party line is this: you don't do good works in order to be convinced of your salvation. Rather, once you have received salvation through faith, the Spirit works in your life to help you grow in your sanctification, and you live a life of gratitude to God for what he has done for you. It's like James says, without works faith is dead. Faith can't exist without works because real faith can't not bear fruit in sanctification. Loving God and neighbor is essential to faith.

But I just can't escape this sinking feeling that somehow my salvation depends on me. This is why: every day we are faced with decisions that we need to make. We have sins that we can avoid. We have oppourtunities to do good works. We could be lazy and sit around. Or we could put our faith into action and do whatever it is God places before us to do. Why does it seem like my decision to do or not do a particular work depends on my me? Why is there even a decision to be made? It seems as if the motivation to do good works between Calvinists and semi-Pelagians is really not that different. Whether you do good works to "earn" your salvation or not, you better be out there doing them because if you're not, then you are not saved or elect.

For the Belgic Confession's Answer to this question, see Belgic Confession Articles 17-24