Who doesn't advocate traveling and especially living abroad? Everyone, it seems. I do. "Just go do it" is the travel advice most people need to hear.
But there are some who take the advice to an extreme. They become professional vagabonds. They backpack around for years, going from hostel to hostel, teaching English in Peru, working at a bookstore in Calcutta. Or there are the international elite who pick a career (e.g. consulting) that requires moving base camps every few years, even within their own country. Or there are the children of diplomats who grow up citizens of the world.
I envy much about how these people live their lives, but when I observe unhappiness, it can usually be traced back to one or more of these three issues:
"Home" changes over the course of one's life. It starts at your place of birth. Half of Americans live within 50 miles of their birthplace. For the other half, what you consider home evolves over the course of time. The most comfortable transition is when "home" goes from A to B with no interlude. You might grow up in San Francisco (home), then move to Los Angeles (SF still home for awhile), until one day you realize that "home" is LA. Boom. It switches. But if you grow up in San Francisco (home), then move to LA, then move to Chicago, then Beijing, then Sydney, at some point SF no longer feels like home, but nor do any of the other cities. Where is your hearth? Where do you go for nurturance and renewal?
Shallowness of relationships
The best way to build intimacy in a relationship is to spend quality in-the-flesh time with each other. If you're always on the go, or never in the same place for more than a few years, intimacy can be hard to come by. It's hard to involve yourself in a long-term relationship if you're nomadic. It's true even for friendships. Thanks to technology it's rare that a friendship would ever move backwards in the absence of physical interaction — maintenance is easy these days — but technology can not accelerate intimacy in the way physicality does. It can even be hard to motivate yourself to invest in relationships as you think to yourself, "I'm leaving in six months anyway, what's the point in trying to find a best friend?" (People who have issues with intimacy of course will embrace this aspect of the traveler's life.)
Where do I belong? Does the country name on my passport still accurately reflect my deepest national ties? How do I answer the question, "Where are you from?" If I'm living in a country where I am not a native speaker, will I ever be treated as a local?
By the way, the best way to understand a serial traveler or expat is to understand what they're escaping from back home. Oppressive parents? Unsuccessful social life? Failure? Racism? Unbearable boredom? Escapism is common to all. Then again, perhaps we're all trying to escape from something…
(tks Maria P. for helping brainstorm this)