I'm not going to go into the indignities of travel, and if you are the kind of dedicated family member who makes the dutiful schlep during the holiday season (I'm not; I consider Nov. 20-Jan. 10 to be a no-fly zone in my year), you need ALL the help you can get. Here's my list of travel day must-haves, which should help with the most common discomforts. Bon voyage!
In-ear or ear-covering headphones: I don't even travel locally without these; the idea of being on a public transportation system without something to block people out causes a panic in my heart. Keeping other's annoying mobile-phone conversations out and away, blocking the yammering of children and crying babies, and fending off random conversation with bored grandmas — headphones do all of these things and also provide you with your favorite tunes, an absorbing podcast (my faves here), or a recorded book by your favorite author. As a woman I also actively "use" my headphones to ignore untoward comments from men. It simultaneously keeps me from feeling degraded (since I can't hear) and secondarily removes the power from the one speaking the words (since I can't hear).
On paper reading material: E-readers like the Kindle and Nook are great, but when you have many hours of transit and limited recharging ability (not to mention all flying time when devices are decreed powered off), dead tree reading is a safer bet. I always pack at least two books and three previously unread magazines, but I'm a little crazy, needing to have one of each genre and something foreign at all times. But bring at least one book and one mag and you'll be protected from boring customs and security lines, too (where electronics are also frowned upon).
Healthy, filling snacks: Don't make the mistake of "picking something up at the airport" unless you know it well. (I know I can depend on JetBlue's JFK terminal and the PDX's offerings, but it's so easy to get screwed at an unknown airport.) While food offerings have gotten better in recent years, it's still mighty disconcerting to realize there's no food offered inflight and nothing edible in the airport either. I always carry Kind bars (they're kind of like my crack; I must always have one around, but any nut bar offers plenty of taste, a hit of protein, and doesn't get squishy or weird-textured). Also, dried fruit, good quality, organic dark chocolate, and a tough fruit like a banana, orange or apple. Check out this great piece by Michelle Higgens for the New York Times Travel section for more great options.
Reusable water bottle: Contrary to what I often hear random fellow passengers saying (when I take my headphones off long enough to hear them), yes, you can bring water bottles through security and onto your plane — they simply have to be empty when you have your always-pleasant visit with the TSA. Once through, you can fill it right back up at the water fountain or sink, which I find necessary, as most airlines don't serve as much water as they used to. Keeping hydrated is a good way to avoid getting ill while traveling — dry mucous membranes in the nose and throat are more susceptible to germs.
Inflatable neck pillow: It's hard to get any real rest while sitting up, whether in a car, plane or train, with your neck craned to one side or the other. A number of companies make already-filled neck pillows, but they are terribly bulky and make adults look like toddlers toting around stuffed animals. A much more travel-friendly and compact version is an inflatable neck pillow that takes four or five deep breaths to fill. They used to give these away on Pan Am in the '80s (along with free ice cream, activities for kids, and legroom, sigh). These days, one has to bring one's own — natch. You can get the basic version for less than $10 at REI, which is really all you need. But this one from Magellan that's got a moisture-wicking jersey (for hot/damp situations) on one side and cozy sueded microfiber on the other is pretty cool and at twice the price, might — or might not — be worth it. Either way, I highly recommend these pillows. Your neck will thank you, and you'll probably rest more soundly, too.
An extra pair of thick, comfy socks: Maybe it's just me, but if my feet are happy, I'm more likely to be happy, too. And socks seem to get so grotty when traveling, for some reason. Whether it's changing into them before arrival at my destination, or an extra layer over my feet at 38,000 feet, more socks are better.