Of Jet Lag
Jet lag is not so bad going west, like America -> Asia or Europe -> America. It's just like having one day that's much longer than usual. You stay awake until it's bedtime in your new time zone, then pass out and sleep till morning, then you're pretty much good to go, although you'll be waking up at the crack of dawn for a while.
It's much much worse going east, like America -> Europe. Instead of having a day that's much longer than usual, you fast-forward through a very short night, and then things get confusing. When it's bedtime in your new time zone you're not tired yet; you can't sleep, so you stay awake in bed until five in the morning, and then when you finally fall asleep you have to get up again in three hours, and then you're all sleep deprived and falling asleep at two in the afternoon. It sucks! It always takes me much longer to recover from than the westward-traveling jet lag.