Personality is the feeling that 'me' is your true self.
The feeling of 'me' is created via internal talk, or thinking to yourself with one's internal commentary about everything you encounter. Then from this incessant talk, feelings are generated according to what you are thinking. Good, bad, like, dislike, anger, happy, etc.
These feelings acutally energize your body muscles, thus you feel alive with whatever feeling you have.
the reason it is like this, is because you are not able to observe your own thinking and feelings and how you are reacting out of it. it's like living in a daydream or a story which you are constantly making up and altering when needed.
Thus the concept of personality is that you exist as this entity, which is actually only attachment to thoughts and feelings, or what you brain is capable of doing via it's mirroring nuerons. we learn by imitation, and then we become imitators, not realizing there is more underneath.