Perhaps, since there are "fundamental difference(s) between humans" some can choose what to feel and think and others cannot. How would anyone other than the individual know? Or for that matter how would any individual know; since for all they know they might feel and think that they choose to feel and think what they feel and think, but they might be one of the poor souls who feel and think that because they have no choice about it. :-} :s ;) >:O

I don't usually quote Schopenhauer, but this quote is pertinent:

Man can do what he wills but he cannot will what he wills.

The limitation on our freedom to will whatever we would will is pretty straightforward:

Long before we are mature enough to make a serious choice, genetics, prenatal environment, upbringing, influence of peers, and so on have shaped us. These limiting factors impose severe limitations on our freedom to "will whatever we want to will".