No purity in change

It's strange how people's personalities change when they assume different roles in life; a person behavior normally differs from when they're in work to when they're at home to when they're with friends and so on. Yet, the core of the person is supposed to stay the same. Every time I think of that, I remember the history books we used to study at school and how they would always say that although Egypt has seen many attacks on it from foreign enemies as well as being colonized since the beginning of time, Egypt has also been successful at preserving its heritage. Whether I agree or not with this statement, it's not the issue, but I've always believed that no matter how tough you are, how consistent or how decisive, your core will always be affected by the tiny little changes going on outside of you, but maybe through cumulative effect rather than a direct one.