Rather than asking ‘how did I come to this belief’ (which may be irrelevant — we can accidentally…

Rather than asking ‘how did I come to this belief’ (which may be irrelevant — we can accidentally stumble upon truths without valid justification, and we can easily have reasonable-sounding justifications for false or unreliable ideas), you might be better of asking ‘under what circumstances does this not hold?’ This is called abductive reasoning, & is the basis of the scientific method.