Do you prefer chocolate or vanilla ice-cream, coffee or tea? Can you will yourself to feel differently about your gustatory preferences?
Your answer probably is that you cannot easily modify any of your basic functions or preferences. Your preferences could be impacted if a highly negative event were closely associated with your eating or drinking a current favorite, but the negative effect would almost certainly gradually wear off with time, restoring your preferences.
For the most part, it is highly convenient not to need to think about controlling respiration, heart rate, intestinal peristalsis, or hormone secretion. You can concentrate on other things and let your brain control those functions. Since you like what you like and are likely to find toxic substances disgusting, you are probably content with your preferences and dislikes.
For the sake of illustration, I have deliberately chosen rather primitive, hard-wired brain activities that are centered in evolutionarily older brain structures – approximately the blue areas in the image. We do not even have the illusion of having free will regarding these brain activities, so deterministic input-effect-effect-effect-output neural sequences are adequate to explain the functions. We don't control them, they control themselves.
Does this mean that we really don't have the free will that theists claim God gave us?
Well, there are no gods to give us free will, so does this mean that we could not have free will at all?
I'll leave you to ponder this question while I take my tired neurons off to sleep, perchance to dream.