If the human brain functions more or less according to classical physics, with causality running forwards in time, then "one's nature" is just a very complicated function of the local state of the universe - the previous state of one's brain (including the encoding of the consciousness function itself) plus incoming sensory data.
More than once you've probably made a decision, at least in part, by psychoanalyzing yourself (and maybe psychoanalyzing the way that you're psychoanalyzing yourself) - so imagine being able to psychoanalyze yourself in real time, with (near-)perfect accuracy. (There might be information-theoretic problems with trying to simulate your whole brain inside of itself at speed.)
If one is the kind of person who has given serious thought to one's motivations in life (which must include coming to the realization that they are, in a certain fundamental sense, arbitrary) then I don't know that they would necessarily change all that much under these conditions.
More than once you've probably made a decision, at least in part, by psychoanalyzing yourself (and maybe psychoanalyzing the way that you're psychoanalyzing yourself) - so imagine being able to psychoanalyze yourself in real time, with (near-)perfect accuracy. (There might be information-theoretic problems with trying to simulate your whole brain inside of itself at speed.)
If one is the kind of person who has given serious thought to one's motivations in life (which must include coming to the realization that they are, in a certain fundamental sense, arbitrary) then I don't know that they would necessarily change all that much under these conditions.