Personality is merely the way we interact with the outside world. Personality is an artifact, a thing, while we are persons. We go far, far deeper than personality. Personality is merely the flotsam and jetsam of life.
However if we are socially mobile upwards, if we want to get on, if we want to get ahead, we will naturally focus on our personality as a tool. And if we are to make it, we even think of changing our personality. Gosh, we will even think of re-inventing ourselves.
If we want to make it, we know we must sell ourselves. And if they aren't buying our old personality, why, we will retool and invent a new personality.
For in the final analysis we are commodities in the consumer society, and we are consumed along with everything else. And so we become things, we reify ourselves, the better to get on. And slowly our personalities harden to form a protective shell and we become a thing that can be bought and sold like any other old thing.