my biggest fear at the moment is having a brain tumor so i'm no stranger to worrying about seizures. any time i start feeling "out of it" or sort of foggy or jittery, i start obsessing over possibly having a seizure. i've never had one in my life but it's the tiny seizures that scare me the most because i don't know what they look like or how they manifest and i'm too scared to google them (which is probably good). so i just assume i have like twenty tiny seizures a day without knowing it.
on another note, back when i had a fear of heart attacks, i experienced chest pain and even developed costochondritis (totally benign condition but painful as hell) from hyperventilating during my panic attacks. once the heart attack fear went away, so did all the symptoms.