Moon and Mercury

Something I don't understand and maybe someone can inform me. If our emotions comes from the position of our moon and our communication comes from Mercury, then what does it really matter where our Sun is when it comes to encountering people and their behaviour? Yet, it's obvious when talking to people, whether they are acting like a Virgo, Pisces, Cancer, etc.

Does this mean that how we feel doesn't matter? We will express it differently because of where our sun is located? So, in essence, everytime we encounter someone and tell them how we feel, we aren't telling the truth? Unless, of course, your moon and sun is in the same position. And when we communicate with people, isn't it about Mercury's position?

So, how can I say I'm a Pisces when really I'm not. I'm where my moon and venus are positioned if that's my true emotional side. Yet, I behave like a Pisces, for the most part, with my Mercury definitely in Aries since I'm confrontational and firey in my verbal pursuits. But, my moon is not Piscean, isn't that who I really am?

I'm sure someone knows these answers.

Our sun sign is the base and everything else is put into the mix in a blending type thing.Yes,your sun has an effect on how you may think or feel and vice versa,I have came across a few sites that do that also the trines,conjuntions,etc. have an effect on it too.