Exhaustion
[send me an emotion and i’ll describe how my muse expresses it non-verbally]
Vulcans do not need as much sleep as humans, this is a known fact. It is also one that Spock had been known to rely on far too heavily on more than one occasion. He is, after all, only half Vulcan. And even full blooded ones do in fact require sleep at some point.
But Spock will pretend otherwise, and use his biology as an excuse when caught up in research or finding some vital information that they need, or just about anything his mood takes to.
Exhaustion is a feeling he knows well. It’s right there in the uncharacteristic slope of his shoulders when he isn’t concentrating on his posture - something that usually comes as naturally as breathing after years of practice. It’s in the way he doesn’t respond as fast as he usually might, and how sometimes his gaze is just caught on something that isn’t there, a fixed point on the wall opposite or the screen he’s staring right through, attempting some form of on the spot sleep-reviving meditation or something.
At it’s worst, he may become irritable if interrupted, stubborn that he can absolutely finish his work before he takes a break, thank you for asking. He may forget his grip on something, his very brief moments of just resting his eyes coming to a stop when his pen clattered against the table.
It usually culminates in passing out on a lab bench or something, often still holding some PADD he’s working on.
