What is a limiting belief?

Belief is something that you believe and it is true. While limiting belief is something we have felt at the rejection or obstacles to achieve a target that you want. Rejection is also arise when we want to change. Also called the (Mental block)

Example of confidence that impedes; I can not become a book author Because I'm not
university graduates. I want to run but can not because I already too old. Whether limiting belief can be changed (Change)?