"These behaviors can be irritating for family members." --on stimming in autistic children

My children stim. I stim--come on, for Pete's sake--every one of us--autistic or not-- STIMS. We all engage in self-regulatory behaviors to calm ourselves. Some of us have small, discrete behaviors that are not necessarily obvious. I swing one of my feet beneath my desk at work. I rub my thumb over my index finger repeatedly. My fingers slide back and forth over the steering wheel while I drive. They're small stims. But they are there, and they are used to regulate myself. 

To take a statement with 'a grain of salt' or 'a pinch of salt' means to accept it but to maintain a degree of skepticism about its truth. --The Phrase Finder

We use idioms with little thought. We know what they mean, even if the saying itself bears no relation to the meaning. Well, except for when that's not true, when we have no idea, when we can't catch the underlying meaning and focus instead on the surface meaning of the words, you know, like my kids do.