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.
Something that I don’t so much believe as assign a higher probability than other people.
There is a limit to how much technology humans can have, how much of the universe we can understand and how complicated of devices we can make. This isn’t necessarily a universal IQ limit but more of an asymptotic limit that our evolved brains can’t surpass. And this limit is lower, perhaps substantially so, than what we would need to do a lot of the cool stuff like achieve the singularity and start colonizing the universe.
I think it’s even possible that some sort of asymptotic limit is common to all evolved life, this may well be a solution to the fermi paradox, not that they aren’t out there, but no one is smart enough to actually leave their rock.