Stimming and how it's helpful. (My friend Josh wrote this and gave me permission to share it here)
I think that many parents/teachers/therapists/etc. don't understand that stimming has any value to the person doing it. They really just don't get that it feels good. That it is calming. That it helps us be more functional. Limiting it to non-destructive/non-disruptive stimming is a reasonable and healthy goal, and so is being able control the stimming for certain circumstances and not freak out if you can't do a certain thing. But the idea that getting ASD folks to stop stimming entirely is part of that wacked out idea that you are going to "cure" Autism. No - you can help folks be happy, well-adjusted Autistics with reasonable means of coping with life's various challenges, but you can't make them not Autistic.
But also, there is a difference between the happy stimming and the "blowing off a little steam" stimming and the frantic "oh god I can't cope and I'm freaking out and all I can do is desperately stim because it is the only thing staving off a complete meltdown" stimming. Try to prevent all stimming, and you tend to end up with none of the "happy stimming" and only these unpredictable bursts of (often really disruptive) stimming which when you try to intervene it results in a complete meltdown. And because so many caregivers don't recognize that even the most destructive/disruptive stimming is generally an attempt at emotional expression or self-regulation, they don't get why the person freaks the fuck out when you stop them from doing it.
I don't stim a whole lot unless I am stressed out or really excited, but being okay with stimming whenever I feel like it has made a huge difference in how calm and focused I am and how well I cope with emotional distress. The other part, though, is understanding what causes the person emotional distress and reducing/eliminating it wherever reasonable, and it ticks me off when therapists are more concerned that the person doesn't "act Autistic" instead of looking at how various things (like sensory issues) make it so hard for the person to cope.