It's not that we choose what to believe, but rather that we believe according to our choices, and our choices arise from prior choices and experiences etc. All of this adds up to the active interface that we present to the world, which is "attitude" (dynamic posture). By this is meant the tendency to make one set of choices as opposed to another, just as a person who leans over in an unsteady attitude (posture) tends to fall in certain directions rather than others.
The "stuff" of which the "self" is composed is entropy, pure information, existing not necessarily in the world as energy, but in potential state space as the potentiality to enter into relationships and thus expand its nature. (Seems like the soul is a thermodynamic system in imaginary space.)
The "self" is is a dynamic, always seeking equilibrium - by eating, metabolizing, breathing, choosing, acting - and thus is reducible to attitude, in the dynamic sense, plus whatever vehicle it happens to be manifested in. In spirit, this is by the support and definition of the spiritual context. Your venerable Chinese ancestor had the same general attitude as does her presently reborn embodiment as your American uncle, with the exception of growth, which tempers all the rough edges through experience.
There is no "storage area" for used personalities to which one might revert. What you are right now is what you are. You can't go back because there is no way to reverse time by more than a few microseconds. (That's because history is pretty well crystallized, and cannot be altered, so time reversal looks like a problem in changing the entire universe to energy and reshaping it.) Instead, history defines us and the space in which we operate, and here we are!
Umpteen rebirths later, the core of the personality will be about the same, although the rest will have become more enlightened, more skilled, more competent and so on. Of course, for some who seem to have been born under a malefic star, the core can be altered as well, all the way down to the first instant that the Creator utters it, "Thou art" .
dave