I was wrong about the reason.
I woke up today feeling really sick. I ignored it, because I always feel a little bit sick in the morning, so what's a little more sickness than I usually feel? It usually goes away anyway, and even though this sickness persisted, I thought it would just go away once I hit an hour I normally wake at.
I went to the Y for my tae kwon do workout, and the sickness briefly felt gone...but then it got worse. Much, much worse.
And ultimately?
I vomited.
Only once, but that's because there was nothing else for me to vomit up.
I have had brief periods where I thought it was just a momentary sickness. That I was making it up, that it was not as bad as I thought, that I was just having bouts of sickness and was actually just fine. Periods where in that bout I thought that I would be fine, I would recover, I was actually well, and I could go on with my day.
...And then the waves of sickness hit me strongly as a reminder that no. I am not imagining it. I am not exaggerating it. I am not making it up. I am not temporarily sick. I am just flat-out outright sick. Sick to the point where I can't even drink water without the risk of vomiting. No joke, I put a single mouthful of water into my mouth...and then immediately spit it out when my body warned me that if I swallowed it wouldn't stay down.
Reflexively I just knew.
Just...ugh, I'd have preferred the suckiness of working to the suckiness of vomiting-sickness.