Like JW's, atheists believe what they say is true at the time that they speak it, albeit for different reasons. For the JW it is because the Watchtower currently says something. For the atheist, he imagines himself as autonomous and therefore the originator of truth.
And you "believe" things because you read it in an old book that is full of self contradictions and has not one single accurate prophecy in it. And why not the Koran? Because you're in freakin dumbass Texas and that's what all the other rednecks believe that's why.
...but we have all suffered from "stinkin thinking", many of us were lobotomized from birth with this kind of relative truth. I personally am done with it...
Finally a bit of honesty. You'd rather "believe" than think. It doesn't hurt as much to stay inside your cuddly little jesus place.