(Not edited, some possible additions)
A belief is an interpretation of how things work that has risen to a feeling of certainty. Until it is supported by the truth, it is not a truth. And all beliefs can be tested by using the scientific method, though many people seem to believe in using the "unscientific method", including "intuition" and "just knowing it is true".
As most people know, we often come to our "conclusion" about something (our belief) and then we selectively seek to find evidence that supports that conclusion. One of the primary contributions, I believe, of Landmark Education and a few other excellent life education workshop organizations is that of having people realize that the evidence is selective and that the beliefs might not be the truth. Before that, there were many participants who believed that their beliefs were "truth" and that there was plenty of evidence to support them! After than, the participants became much more open and were much better learners and changers of beliefs.
And sometimes we arrive at our faith in one belief through the use of other beliefs that support that belief. Sometimes, we even derive a belief from other beliefs.
Imagine that, we construct something that we believe is the truth from other beliefs that may not be the truth. Disaster city!
And it is true that many of our beliefs cause disasters - which are usually only emotional disasters, though they occasionally have us behave in a way that creates physically manifested bad results.
As a child, my Mom told us we had to be kind to other people. She also seemed so anxious in general that I felt helpless to help her, as I believed that it was my duty to do so and that I somehow had the power to do that. Since I believed that I had such power and since she was still anxious, I developed guilt over anyone feeling bad around me and believed it was my fault for not having corrected it. And since I had to be nice to people, I tried to smooth everything over and was afraid to be daring with people or even to express my own needs, such as having to go to the bathroom - so I "held" it.
And then I grew to be a bashful, awkward boy and young man, with little self confidence, but that is another story based on beliefs.
When I saw that they were just beliefs and then tested each one of them with the Truth Test "Is this true, absolutely true?", I began my journey back to my potential. This was the beginning, as I needed to replace those beliefs with new ones. Unfortunately, I delayed getting around to it, and created needless periods of not yet being as confident as I could be.
Another friend of mine had the following "story", which she fully believed, even though "intellectually" she said she knew better. When I use the term in my theoretical quote here of "made up" I have substituted what is actually the case, though my friend believed her beliefs to be the truth and that created her being the victim of it. "My mother always compared me to a friend's daughter, mostly unfavorably. So I figured that I was inferior and would never be good enough. At that age I was so vulnerable that I had to have her love me - and if she didn't the "worst would happen". [A child often catastrophizes because of a feeling of being overwhelmed if anything goes wrong, as he/she feels she cannot cope with or have power over circumstances.) She compared me to my brother, too. And then I could see that she was so perfect and so admired by others, so I made up that I had to be as good as her to be "good enough". I was trapped by her having to say something good about me and trying to please her, but I never seemed to be able to please her. That's why I am the way I am. [That's a belief, not a given, as she has a say, at some point, in changing the belief.] My mother was always talking about smart people, successful people, accomplished people, literate people, powerful people - so I made up that I needed to be those in order to be "ok" and not just shrivel up and die, since I could never prove I deserved to be alive." And the saga goes on beyond that.
But now in public if she meets anyone who is of status, she goes into a belief that she is doomed if she doesn't get their approval and that she is inferior so she has to pretend and put up a good front. Her belief that she is doomed is supported by the fact that she goes into panic attacks and is wiped out afterwards.
She believes that we need approval from others to be good enough. Supporting her not being good enough is her belief that she did not measure up to the friend's daughter or her brother. Supporting her need for others to approve is the belief that she is not good enough if someone else is more literate or accomplished and they do not see her as such.
The point here is that the supporting beliefs and evidence are what holds up the big belief of "needing approval" (or the bigger one of still believing she is a child). However, the supporting beliefs are so fragile and so untrue that the minute she thoroughly faces them and rewrites them to what is true, the bigger beliefs will fall.
The interesting thing is that those same supporting beliefs, in different combinations, support other beliefs, so that once we actually change a belief it becomes like a house of cards or dominoes falling over and knocking the other ones over.
It is interesting to hear of how she diminishes her accomplishments, her knowledge, and her contribution to others - all because of her belief structure.