@killo,
but maybe we have no free will, or don't make our own decisions.
there are a few possible (and plausible) theories which could strip us of freewill, and decision making. two of these are:
the multiverse: in an infinite multiverse made up of a finite set of fundamental particles, entire universes repeat infinitely, along with ALL POSSIBLE variations (imagine dealing out an infinite number of packs of shuffled playing cards. because each pack consists of only 52 cards, at some point, more than once, infinitely even, you would deal a pack in order). therefore anything possible exists infinitely. if we "make" a decision, then by extension, all possible variations of us need to also take every possible decision. this removes choice, as all roles have to be filled, so the last one (not that there could ever be a "last one" but for the sake of this analogy...)the last one cannot say "no thankyou". something must accept it. it could be that we are a fluke, and the only universe to be made up exactly as it is,to the last particle, and for one possible universe to not exist yet by one particle, but when we are talking of infinite proportions, our choices are so small as to be rendered obsolete. one TINY variation, one particle, is all it takes but in an infinity of variations, the probability is even smaller.
time and space: according to einstein time IS space. if time is space, then time is everywhere, and space is everywhen. this means the past exists everywhere, and everywhen, as do present and future. this in turn means the future already exists everywhere, again rendering choice obsolete.
in both these scenarios our destinies are pre-determined.