I do not think I am nice.
And: It might be better not to be nice in many situations. Or to make a point of being not-nice (in an innocent way), because otherwise some unwanted admirer who will not take a no for an answer (because in his culture women have no brains and do not know what they want) will get on your nervers.
We are attracted to some people and repelled by other people. This is unconscious. Our whole life experience participates in this decision. We express our attitude unconsciously too, by the tone of the voice and other signals.
We cannot really control it.
The best we can do is to remain polite. The message is then: I do not like you at all but I make an effort to be polite because I want to belong to a civilized society and I expect you to do the same.
Who is going to cast the first stone on me ?