It turns out that when I’m tired I have fits of hysteria. They consist of bouts of uncontrollable laughter. It’s better than weeping, of course, but it’s not always pleasant, given that it gets to the point where I can’t breathe and can’t stop.
Hysteria
Clarissa's Blog 
Well, at least you don’t scream, which would scare Klara, or smash things, which would be a very counterproductive destruction of property.
I can tell when I’m getting into a non-helpful mood, because my cat starts giving me alarmed stares.
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