Yes, the question does everyone's head in. Determinism should not be confused with fatalism which is about you will end up on the same result. Determinism is trying to live your life with the illusion of free will and is more like Calvinism. Calvinists believe in there being a preset path from God and that in every action you do, it is preordained by God. They say you shouldn't try to think what the mind of God would be like and that any choice, even if you changed your decision when you know the result, will still be predetermined.
Now I won't go into any detail of these matters since they don't need any. Simple idea that is extremely un-falsifiable. Whatever you do, it has been determined from birth. Free will is an illusion of your mind. Now there is proof that for every decision you make, that decision has been made up in your mind through neural stimuli and responses. After the connections are made, THEN you make the decision of suppose eating unknown food A instead of food B, just based on cognitive schema. This frightens people and right should as then we don't have free will. But, you could say you voluntarily make that connection in your head in the 1st place and then think about doing it. Either way, it gets all muddled up and delves into "what if" thinking.
How about we live with the illusion of free will and ignore any people trying to make us think deeply about determinism. What's wrong with that? The point I'm trying to make is determinism basically means you can't help it. Wouldn't this lead everyone to just kill themselves hypothetically and get it over with. Ther will be no purpose to life and no reason to continue the struggle of modern life harships. All these discussions were put forth by a fictional movie we saw shown by our Psychology teacher. However, bad the acting, and overbearing and inappropriate music, the point got through. All of the students said their head was spinning. THen I think what use is it for thinking about it and not getting an answer. Is there any use in worrying about it? Worry is a negative behaviour and we will try to combat it with producing a positive behaviour. In this case, there is no good response just the thought of there is no reason to care.
Again, I say let's live with the free will we think we have. We are probably in metaphorical cages and even if we think we get out we're just in another cage. What if the Matrix was real and we were jacked up and then lived our lives like ignorant bodies that only relied on pleasures and simple matters. Either way, that would be a more functional and purposeful existence and wouldn't lead us to suicide. What good would it do then, if we all killed ourselves on this Earth? Does the universe care? The reason I think for human's existence is to create purpose where it might not be. We are inspirational beings not preordained to think in a fatalistic manner. Maybe that's why we still exist as a species. We might not have the most creative ways of solving problems either evolutionary or socially but we are the only ones who care, or then we'd have other animals as 'intelligent' and us and we'd be the ones in the pinwheel. What if the opposite was completely true? That we have full free will and only alluding ourselves that everything is preordained. Maybe we want order and not chaos so we think there is a design, there is one chosen path, and that there is a resolution. This type of thinking could be as possible.
Impossibility is not in the scientific dictionary. There is always a chance some event might occur in the universe no matter how low a probability. It could be possible there is a gene for certain behaviours and actions we'll do. Then what? Environment might influence it sure, but that then is again predetermined. Eventually, you'll realise philosophers are hopeless thinkers. We can ask the best of questions and still not get an answer ever. If you think about it, anyone can do that. They just need to inventive enough to create a plausible response to anyone doubting and asking the conflicting question. Let all the people who want to believe in determinism, calvinism, fatalism, let them think it. This would be tolerance and another way of creating order for ourselves. This issue spills into other debates such as order and choas, control from the government or our free choice to abide by the law. My own opinion is not to worry your head over such trivial matters. These are all in the realm of philosophy where endless circles roam and questions are more important. Even in the future we find out that we can predict a person's life through genes like Minority Report, we can still be comfortable in the fact that the illusion of free will still gives us pleasures, rewards, and experience. Yes, a very confused conclusion but you'll never satisfy all the bounds of philosophy.