Race against the clock, but the clock is their own failing body.
Medic who catches the same disease their patients have, and knows its progression intimately, and is determined to continue caring for their patients as long as they possibly can.
In a similar vein, a spy or assassin who knows they've been poisoned (with a poison they've used before...?) but must complete the mission and get to safety without arousing suspicion.
SELF SURGERY this is the self surgery trope this is THEEE self surgery trope my friends. <3.
Adrenaline high, temporary pain relief, superpower that holds off injury... and Whumpee pushing themself as far as they possibly can, because they know once it wears off, they're not getting back up again. (may or may not be inspired by @tired-of-being-nice's Coren...)
And the core appeal, for me, is Whumpee planning for their deteriorating condition.
It's the acceptance! The inevitability! And the determination to keep going anyway - in the face of inevitability, still giving it their best shot.
Whumpee pushing themself harder once they realise they're ill, stacking the most demanding tasks back-to-back to get them out of the way while they still can.
Planning for specific symptoms, not just severity: "in a few hours my vision will go blurry, so I need to get all the paperwork done before then."
Last-minute instructing an ally - if they are lucky enough to have one - how to continue their mission, treat their patients, etc, and the ally's growing panic: "Just tell me how I can help you!" "Don't- [cough] - worry about me. Listen."
Pre-emptively putting water and meds in reach because they won't be getting up again; they'll be lucky to move at all. (This was definitely inspired by @chiswhumpcorner's Kev.)
Laying down moments before they fall down...
