Play Tetris (or any similar activity that requires a good deal of concentration) seriously it really works. Playing Testris has cured many a bad trip for me personally and a few times it has even helped me calm my thoughts to a point where I was able to enjoy the high. It doesn't sober you up but it does makes time fly by and distracts your mind.

It's a form of misdirection and meditative concentration. I contribute alot of the discomforts from a bad trip to be psychological. If you can distract your mind from the uncomfortable 'feelings', it will take the edge off your bad high quite a bit.

Good luck dude.