Determinism, predestination, etc. seem to go hand in hand. The Stanford Encyclopedia of Philosophy says of determination and human free agency:
… It is hard to see how, if the state of the world 1000 years ago fixes everything I do during my life, I can meaningfully say that I am a free agent, the author of my own actions, which I could have freely chosen to perform differently. After all, I have neither the power to change the laws of nature, nor to change the past! So in what sense can I attribute freedom of choice to myself?
So this is a purely philosophical question for some, like at Stanford. But for others, like in Christianity, and in particular, within Reformed Christianity, it is a deeply theological question. The famous 17th Century document, the Westminster Confession of Faith says this of God’s decrees and ordination of things:
I. God from all eternity, did, by the most wise and holy counsel of His own will, freely, and unchangeably ordain whatsoever comes to pass; yet so, as thereby neither is God the author of sin, nor is violence offered to the will of the creatures; nor is the liberty or contingency of second causes taken away, but rather established.
II. Although God knows whatsoever may or can come to pass upon all supposed conditions; yet has He not decreed anything because He foresaw it as future, or as that which would come to pass upon such conditions.
III. By the decree of God, for the manifestation of His glory, some men and angels are predestinated unto everlasting life; and others foreordained to everlasting death.
If I am a Christian, and I affirm an understanding of God like that articulated in the Westminster Confession of Faith (and many do, even people who are simply ‘Evangelical’ Christians), does this mean that if I get a terminal diagnosis, like a certain kind of cancer (like the kind I had, Desmoplastic Small Round Cell Tumor sarcoma) that I am doomed? Does this mean that God must have ordained for me to die from this cancer, and that I can do nothing, that there is nothing contingent waiting my actuation of it that might aid in my healing, maybe even of a so called terminal cancer?
I think if we believe in a God who works through deterministic mechanistic decrees, that we, if placed into a health crisis, for example, might very well resign ourselves to the idea that God has decreed my death through the secondary means of whatever my terminal diagnosis is. And so we will begin down this fatalistic path, we will start living into death, instead of living into life.
We still have choices to make in light of our health diagnoses, God has not decreed one outcome, necessarily, over the other; even if he had, how could we ever claim to pierce this remote session of God’s inner life? It is more prudent to cry out to God for wisdom in how to proceed, and not give into a fatalistic understanding of God’s dealings with humanity. We need to take action, and not presume upon God’s sovereignty as if it means that he has dealt us a death blow through him apparently decreeing our demise. Last time I read, he wants us to choose life, not death, and this means rebuking any thought any inkling that God works in fatalistic ways.
Is God sovereign? Indeed. But he does not work deterministically, he works dynamically and personally and relationally as the eternal relation that he is as Father, Son, and Holy Spirit. If you receive a terminal health diagnosis I would like to encourage you to rest in God’s life of Triune love and power, but to take every step at your disposal (even if it means going ‘alternative’) to choose life and not death. Don’t give into theology that makes God out to be something he is not. He is not a determinist, he is a person, and his name is Jesus Christ, full of the life of God for us.
 See full text here, http://plato.stanford.edu/entries/determinism-causal/#DetHumAct
 See full text here, http://www.reformed.org/documents/wcf_with_proofs/