Especially that dihydrogen monoxide

If you keep drilling down on the why you have certain preferences, at the very beginning of the causal chain of events, it is unlikely that choosing to do that thing or preferring that thing was the beginning of it. Evolution, nature/nurture, biology, chemistry, biophysics etc are slowly chipping away at the facade of free will. You do still own your actions because you exist physically in this universe and in your body. But without a supernatural component to the brain (which is totally fine and good to believe in, and I think it's valid and human to have opinions that can't be proved) free will in the truest sense is very unlikely. But this line of reasoning is perhaps an academic and philosophical argument which probably ought not to be inserted into your daily decision tree.