Every breakdown, meltdown and shutdown is a little different and everybody handles them differently. After having one last night and having to explain what happens during it to a close friend who was present, the process is fresh in my mind. If you've ever wondered what's happening in the mind of an Autist or Aspie going through a shutdown, it might be something close to this.
First, there has to be buildup to the trigger. A meltdown can seemingly come from something totally insignificant, but there is usually prior emotional stress which allows the straw to break the camel's back. In this case, it was the combination of being around someone who was stressed out all day and another person becoming angry at me,
Second, the trigger happens. Here it was a minor change of plans. In the sub-second, there's a fear of something happening or not happening. I was afraid that if I did the change, I'd have to talk to or see the person who was angry at me and I wasn't ready for that.
Third, the freeze-up sets in. This is when responsiveness to words and external stimuli slows and the brain is overloaded, unable to process what's happening. The ability to move or speak is greatly reduced, but mental function remains the same. I am well aware of what's going on when I start to melt down and how I'm reacting.
Fourth, if the outside stimulus or overload continues, all external control is gone. I can't speak or move or make any kind of signal of what's going on in my head to the outside world. However, I continue to think clearly and can understand everything which is being said to me or is happening, but I'm not in control of my body. I'll jerk away, tense, cover my head or bite myself and not be able to control it. If I'm asked to move or do something, no matter how much I might want to, I can't. My entire body is tensed and the stimming is stepped up.
Fifth, the tension continues but it doesn't increase any further. No control is regained but none is lost. This can continue for a few minutes to a half an hour.
Sixth, the letdown begins. I start to feel fatigue and pain and regain the ability to move and speak a little. It's easy to go straight back into the overstimulation if something bad happens again. After some time, I'm able to answer questions and might be capable of touching someone again, even if it's just with one finger.
Finally, the sickness comes over me. A meltdown is very painful. My muscles are tensed for an extended period of time, breathing is very shallow and through my mouth, so when I come out if it I feel sick and tired and need to drink something. Sometimes I'll just collapse and sleep for an hour or two straight after one and other times I'll get on with my day but have a headache or stomach problems.
I am entirely aware throughout any kind of meltdown, shutdown or breakdown and yes, if someone does something particularly stupid to me during one, I'm going to remember it and likely resent it. It's very painful not only physically but mentally because I'm so scared by losing that control. I imagine the frustration is much like how it is for those who are entirely non-verbal - I've got lots going on in my head and no way to show or tell anyone else.
This isn't how every person reacts or what they go through, but I hope it spreads some knowledge.