I can't really relate to the religious stories, my parents, though not atheists, are pretty secular so I never had the brush with religious indoctrination. In reality I've probably always been an atheist. I think this gave me an early start on rationality, not so much because atheism taught me rationality, but because I never had to abandon a rational line of thought for fear of challenging my religion.

As for consciously trying to be rational though I don't know of any one defining moment though I can recall a slight watershed. During grade 11 I was selected to go with some other students to an economics conference. The conference was run by a strongly right wing institute and myself being left wing, and wanting to signal my intellect by challenging much older and much more knowledgeable people got into (and probably made a fool of myself in) numerous debates.

I recall over the next several months starting to realize that my own views and conclusions might be mistaken. For the first time I started seriously considering how to actually think about and try to find the truth which is probably the same place I'm at today.