When "it" episodes run riot

Today was just a bad day all around.  Very hot, uncomfortable...and a lot of yard work to do.  I pretty much started feeling the effects immediately.  I was able to finish early, but not early enough, apparently.
Because when I tried to have dinner, my stomach immediately rejected it.  After the first "it" episode, my initial thought was that maybe it was a stress headache.  But normally my head clears after a stress "it", and this time it did not.
So completely did my stomach reject food that I had two more "it" episodes within an hour after the first one.  The only thing I can figure is that I had overexposure to the heat and humidity, exacberated by the fact that I don't have any yard work clothes that aren't dark colored.  So you can actually argue, plausibly, that today I pretty much shot myself in the foot.
This is how it is with me, usually...a slow learner, while most of the time I unconsciously heed warnings about days like these, eventually one comes down the road where for all intents and purposes I have to whiz on the electric fence and find out for myself.  Not the best way to go about things, that's true.