My ex- told me that I had to stop believing in gravity because it's just (her) God pushing down on us. That's why mountains don't pull you towards them. (She cried when I told her about the experiment where just this thing was tested and it was found to be untrue, said something about Satan.)
A friend once told me that meditation allows demons to take over your mind and make you crazy. This guy has a physics PhD, and not only believes this but also that global warming is an evil communist conspiracy designed to steal our freedoms. Not precisely his words, but close enough.
A good friend was told by his girlfriend that she couldn't marry him unless he converted and joined her church. Another of my friends was a member of that church, and won't talk about his time there (he's really messed up, and if you touch him accidentally he almost loses it) but tells me that it's all about control and power.
> My fear is that I'm unknowingly harboring some wildly irrational beliefs.
I have very much the same fear. I know I have held stupid beliefs ("depression isn't real, harden up!" was particularly ironic, as I was depressed, didn't know it, and that attitude was a result).