A paper plane

Science cannot predict where a paper plane is going to land even if the track of it in the air is determined by some laws of physics. The existence of free will might be an illusion in some respects, but pursuing deterministically reductionistic theories is usually a futile attempt.

Predicting the track of a sheet of paper in the air might be more difficult.

I wish I were a paper plane; I am a sheet of paper in the air. I am at the mercy of the wind, but scientists cannot tell where I am going. Thus spoke a sheet of paper.

If you drive a car drunk, you will be arrested, but the car will not be arrested because it is just a machine, although it might be confiscated from you. Our society prohibits drunk driving because it is dangerous to us all. The existence of free will might be an illusion, but you cannot dismiss the idea. Freedom, equality, privacy, and informed consent, and so forth are all ideas. You cannot disregard these ideas because they are not tested by scientific procedures.

"The notion that there is no truly free will . . ." does not have to make you "depressed" because it does not signify that you have no control over your decisions as a human being.

If you are interested in the existence or nonexistence of free will of consumers and producers in commodity markets, you should study not only physics but also economics. I don't think physics is almighty. You should study both macro economics and micro economics, but understanding the mechanism of economies is not enough for predicting the business fluctuations. There is no telling what will happen next year. There is no truly free will in the social world, but if it should exist, it would not be so effective in attaining your own economic goals. Are these things depressing or not?