Pain.

I have a high tolerance of physical pain. After a good workout, or the first after a hiatus, the muscle soreness is not only tolerable, but welcomed. In jointlocks, it takes much more effort to make me tap out, once to the point where I probably injured my elbow from stubbornness. But there's one type of pain that takes me straight to my limit: gas pains.

I had a grueling experience just yesterday where I had a near mental shutdown from an excruciating torment deep behind my solarplexes. It completely stopped me from being able to do any work. During this kind of knee-weakening, back-arching pain, any burp, any flatulance means instant relief. The bigger the better, the more the merrier. There is no time when you find more pleasure in your bodily functions than when taken by gas pains. But the relief is always temporary, and gas pains often last a couple days. Fortunately, in these cases, I can find asylum in OTC drugs like Gascon and Gas-X.