What do you want to believe? You should really give that question some serious thought before you ever look at the evidence in a given case. Because what you want to believe is like a giant thumb on the scales as you balance the evidence before you.
People commonly sweep incontrovertible evidence under the rug in order to believe what they want to believe. And perhaps, when you are trying to understand some egregiously stupid behavior on the part of a friend, just ask yourself,
What do they want to believe?
Another, more life-affecting question is this:
Why, so often, would we rather believe a lie than to believe God?