We create beliefs to anchor our understanding of the world around us and so, once we have formed a belief, we will tend to persevere with that belief.
What Are Beliefs?
Here's a simple definition: A belief is an assumed truth.
Hence everything is a belief -- including this statement.
Your belief system gives you a framework that helps you interpret and understand the experiences you face in life. A belief is something you accept as true, without question.
That means you can expect that every day it will seem just as true as it was the day before.
Your beliefs are deeply embedded in you, so you and particularly your team of protective inner selves, live your life around them, without thinking about them, questioning them or even being aware of them.
As part of your overall belief system you may, as a small child, have developed unbalanced or negative beliefs about yourself, that actually helped you ‘fit in’ to your family environment by making sense of things that happened to you, things that would otherwise be very hard for you to live with. For example if, a small child is constantly ignored or neglected, one of his or her beliefs might be ‘I am not worthwhile’.
The corollary of our definition of belief is that if we know something to be true, then it is more than a belief. The tricky question now is 'How do we know that something is always true?' Just because in our experience it has always been true, it doesn't necessarily follow that it will continue to be true.
We usually belief that things will happen as they have previously happened, because it is useful to do so. As such, this means that everything is a belief. Which is good, from a persuasion standpoint. Because beliefs can be changed.
Beliefs and language
Belief is highly entangled with language. If there is a word for something then we believe it exists, as in the Sapir-Whorf Hypothesis. We thus 'language reality into existence'.
This is one reason why people from different countries have difficulty understanding one another, as the beliefs they hold are built into the language and the culture.
So understand that people's beliefs are what they are assuming to be true. Challenge them. Reframe them. They can be changed.
So our core beliefs as they took root in our first few years became a kind of summary of the most basic convictions we make up about our self-worth, the kind of person we are, what will become of us as a result, our place in the family and the world and how we can expect others to treat us all our life.