Can your personality change? I always used myself as proof that it could, because I now act in completely different ways, love things I hated, hate things I loved, and behave wildly differently. I was proud is of myself and started writing poems about the drunken furor of the will in its grand struggle followed by its triumphal march when it at last wins, but then I realized that the fact that I was quite unhappy when acting the other way but am generally quite happy now might mean there's more to it than I thought.