One of the ongoing problems that we have run into in Thailand is that of heat-exhaustion and/or carsickness. While this ALWAYS sucks, it just seems to be a part of life over here for us, and we just figure out our plans and deal with it as it comes up. Dramamine does help a lot, as does continually drinking just about any liquid we can get our hands on, but some adventures need to be shortened and some situations just... suck.
Having a carsickness induced migraine while waiting for a cab or a train in the middle of a loud city is pretty much the definition of sucky. Oh well, life goes on.