Are we really choosing to believe it or disbelieve what others tell us or what we tell ourselves, or do we believe or disbelieve what others tell us or what we tell ourselves based on our core biases and convictions that are a product of our experiences?
That's a good question. I'd still say we choose to believe or disbelieve. Those core biases and convictions are a part of a feedback system along with beliefs and experiences. It is a self-reinforcing feedback loop, with beliefs choosing thoughts and actions, which create experiences, which inform core values, which inform beliefs, which inform thoughts and actions, and so on and so forth.
It is a cycle that largely remains unexamined in most, simply running the program where we either just keep on course, whether towards the positive, the negative, or just simply maintaining status quo.
But at a certain point, someone can break that patterned response cycle, by an act of the Will. It begins with that
choice. Once that choice is made, then what is allowed to inform the system will be willfully selected. "I want to be happy," means I will choose to not believe in self-defeating negative things. That will then affect my experiences, which will in turn affect my core biases and values, which will then continue to choose to believe positive things rather than negative; and on it goes into a new patterned response.
If someone is not actively, or consciously choosing at the moment, and are simply running the habituated response programs, they are implicitly choosing every time to continue that patterned response. They are simply choosing to let it run.
Hopefully that gives a better description of why I am saying that choice is always present, whether actively or passively. To actively choose with the Will to change that cycle, is what leads to radical transformation. We begin to wake up to ourselves and see we have a choice of what we want to believe in.