Hit the panic button!
Imagine the scene: you're walking along a path looking at the elevation app on your phone that gives you a continuous readout of your height above sea level. As you walk up a hill, your elevation increases smoothly with each step you take. Then you're surprised to find that one more step has caused your elevation to change suddenly to 50 metres below where it was. What has happened?
In mathematical terms you have passed through a "fold-type catastrophe". In everyday language you've walked off a cliff!
This behaviour, where some property responds smoothly to a varying stimulus, up to a point where it suddenly jumps to a new state, is quite common. A rubber band stretches under increasing load until it snaps. A brick standing on end tilts more and more if it's pushed sideways and then topples.
And we see it in human behaviour: when pressure builds - it starts as a minor irritation that gets more and more uncomfortable until, like the rubber band, you snap. Violent outbursts can erupt without warning. For instance, someone endures jibes and insults at work for weeks with no sign of being affected by them and then suddenly explodes - or breaks down in tears.
In a crisis situation, the demands placed on individuals can multiply rapidly until they can no longer be dealt with. You're probably familiar with that feeling of being swamped when you suddenly can't cope. You have reached the limit of your mental resources.
I think that all of the examples of a person's emotional state suddenly flipping are symptomatic of overwhelm.
If your PC has too many things to do at once it will slow down as its memory is filled up or its processor is engaged 100%. I suppose this might happen in humans too (whatever the neurological equivalent of "processor" is) but I think that when we freeze up it's more likely that it's a sign of lack of an appropriate program to run. Psychologists and therapists talk about "coping strategies" that their patients can employ to deal with their particular challenges. And strategies, in this context, are "ways of doing things" - in computer-speak they are algorithms or programs.
You'll recall from past articles that I like to think of almost everything that you or I do as being driven by mental patterns that we've learned by experience. And most of the time they are unconscious - they run without you being aware of them.
Now, if you're suffering bullying or provocation you will be aware of it, and you may feel the snapping point approaching. But what if you're completely absorbed in dealing with a problem that is escalating? You'll be employing strategies without knowing it, simply responding to each demand in your usual way.
You handle the increasing complexity until, suddenly, you can no longer do it. You don't have a strategy for the latest complication and you freeze and panic.
A well designed engineering system will respond to overload by selectively switching off "services" in order to maintain its overall function. A poorly designed system simply crashes.
What's the human equivalent of switching off services as an alternative to crashing? The detail depends on the context: maybe you re-assess priorities, or you call your boss for instructions, or you ask for assistance from anyone else who isn't overwhelmed.
In general, what you do is just another strategy! A fallback that you pull out when all else has failed.
From a management or coaching point of view, you can look out for the signs of overwhelm in others. It's not the same as being overstretched long term, so that they miss targets or work excessive hours. Rather it's their response to a particular situation that might crop up during an otherwise comfortable period. You may not be able to intervene at the time, but afterwards you can coach them to develop (and practise) a fallback strategy to use next time.
To push the computer analogy for all it's worth, you don't need to replace the person you just need to upgrade their software. With their permission of course!