Part of our human nature is to hold beliefs as the ultimate indicators of truth. This creates a tendency to disregard or question any facts to the contrary. We believe what we want to believe, which in many cases is what we have always believed. This is the legitimacy of familiarity.
One way to escape this is by translating beliefs as assumptions into questions. As soon as we have a question, our mind becomes interested rather than certain. And in interest, new things become possible.