We are primed to see and agree with ideas that fit our preconceptions, and to ignore and dismiss information that conflicts with them. You could say that this is the mother of all biases, as it affects so much of our thinking through motivated reasoning. To help counteract its influence we ought to presume ourselves wrong until proven right.
Think of your ideas and beliefs as software you’re actively trying to find problems with rather than things to be defended. “The first principle is that you must not fool yourself – and you are the easiest person to fool.” - Richard Feynman