Try channeling it into something useful, like hitting a punching bag or sprinting round the block. I find that running helps me burn off most of my meltdown feelings because afterward I'm too tired to get physically violent, and when my actions don't match my thoughts, it's easier to switch the meltdown off. If you need things to do with your hands, tearing up sheets of paper in stacks to give them more resistance can help, as can screwing up and squashing things like soft toys and beanbags, things that won't burst on you when you squeeze them hard. I tend to bite down really hard on my fingers when I'm really angry or gearing up for a meltdown; if you have any tendencies like that, they make rubber chew straws that you can use instead... I may need to look into them before too much longer. Anyway, good luck, meltdowns suck, and people getting mad at you for them definitely doesn't make them any easier.
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"Survival is insufficient" - Seven of Nine
Diagnosed with ASD level 1 on the 10th of April, 2014
Rediagnosed with ASD level 2 on the 4th of May, 2019
Thanks to Olympiadis for my fantastic avatar!