Personal identity is very narrowly defined and people often do exhibit more than one personality.
Philosophically, we are the outcome of socio- environmental conditioning and the experiences of our life that moulds our views of the world.To an extent there is a great degree of indoctrination as well.
Scientifically, our personality is the outcome of how our brains are wired.
This would depend on the conditional hypothesis. If I am to assume
A)All pretty girls wear daisies in their hair then the first instance is correct.
B)If a different brain would change your taste perception to be favorable towards pizzas then the second instance could also be true.
Thus both statements are valid and capable of being true or false.
For that to be the case, you had to assume that I could
be a girl or have a different brain. If personal identity was only a (by)product of a particular neural network, "I" would be very narrowly defined. As a matter of fact, I can't even begin to fathom HOW narrowly, if we were to account for changes through time (drastic or otherwise).
If I could be who I am not, there is more to being
someone than just a skullful of squishy matter. It is, of course, extremely difficult to verbalize this clearly... but we are looking through SOMEONE'S eyes, aren't we ? It might have as well been someone else's and we'd see different sights, likely have different memories (maybe harbor an uncanny fondness for daisies, who knows ?)... but it could be US looking.