One of the most frustrating things about traveling between continents is jet lag. It's a little different for everyone but basically is caused by your body's 24 bio-rhythm (internal clock) being thrown into disarray by changing time zones, disrupted patterns of eating and sleeping, and altered exercise routines. Some say dehydration caused by air travel contributes and it probably does (so drink water and avoid too much caffeine and alcohol). Experienced business traveler Songhua Ni sleeps as much as he can while flying to beat his jet lag, as he shares with the Wall Street Journal in this article.
To make matters worse, once you've adjusted to that foreign time zone, your vacation ends and you return home and repeat the cycle of jet lag.
I've found no great cure. I tend to try to nap on the plane, too, but when I land I force myself to get into that local timezone. I don't nap when I land. I tend to get out and walk around for the day, seeing and doing as much as I can. (and physically tiring myself). After dinner I crash and sleep as long as I can. That usually works pretty well, but still I tend to wake up early for a number of days and tiring in the afternoon.
I'm curious what your experience is. How do you deal with jet lag.