Sincerity

How do you really know when someone is sincere? How many times in a day , year, month or life time do you think you have been taken? Is there ever a way to know for sure someone is being sincere? You would think you could trust what you feel but sometimes that's not the case. So how do yo know? Take sex as an example, women are constantly complaining that the man said all the right things and after he got what he wanted the situation changed. Is it possible the women just saw what she wanted to see in the moment? Or was she actually led to believe something false? It’s such as shame that we as a society have become so distrustful. If only things could just be what they actually seem to be.