As a child you come into the world without any idea about anything. You are a born physiologically premature, dependent on your environment for years. When you are born in Spain, you inevitably learn Spanish. German in Germany. If you grow up in a rich family, you learn rich. In a shitty environment: shit.
You are born into culture, society and social circumstances that are given from minute zero. What and how you think and act inevitably follows a script you follow. Every inner voice was an outer voice at some point. Every belief that is crucial to your life results from the script, combined with your experience.
Do your beliefs help you to live your full potential? Or do they hold you back? Are they even harmful? People are evil? Money is bad? Sun makes shadow? Beliefs are like a filter that selects our perception. If there are evil people everywhere with too much money, there are probably your beliefs at work. Your beliefs determine the film of your reality that you see.
The good news is that you can change it. Every inner voice was once an outer voice, but not necessarily yours. When you understand this, you can free yourself from it (and jump back to the previous chapter).