Marx and Althusser - Dot

In the introduction to Marx and Althusser's work readers are presented with the idea of ideology, something I thought I was very familiar with. After reading the introduction, it turns out I am not as sure of my knowledge on the subject as I had previously thought. I was very intrigued by one of Marx's statements which reads "It is not the consciousness of people that determines their being, but, on the contrary, their social being that determines their consciousness" 

In reading this line, I considered the many stipulations that could go along with it. Mainly I thought of my own life and how I rarely realize that things that I do are because of the ideology I participate in. Therefore, how can one tell if something is done out of the influence of ideology or if a person is simply doing something because they think it is what they should do? 

But them, why do they think they should do that particular thing? Who tells us to do the things that we do, is every aspect of our life controlled by the society around? Do we really have any original thoughts? Without ideology how would culture function? Would anything make sense?

As I am sure Marx and Althusser would agree, ideology is an extremely dynamic part of our society that controls all of our actions and thoughts. I am very interested to see how we will discuss this topic in class and how it will be used to further explain post-modernity.