Seriously, it's a bad idea. You never know where it will end up. Of course we all do sometimes, but it's best to make sure you are in a safe location first, no sharp corners, steep drops, speeding trains and the like. If you feel your head coming undone it's best to hurry home (not too fast) and lie down on the couch. Take a nap or read a boring book and then take a nap. Whatever you do, don't wander around tourist areas during such a sensitive experience.