Why does bad shopping happen to good travelers?Lynn Yaegar ponders vacation-induced shopping anxiety.

I had just got off the plane in Tokyo and I was exhausted—so tired that the town, always a little strange, seemed positively surreal—but what was the point of trying to sleep?Instead I headed directly to Loveless, which I had been told was the coolest of the hot stores in the Aoyama neighborhood. And indeed, with its magenta walls and massive chandeliers, its stacks of Goyard valises and racks of McQueen tutus, it was everything I dreamed shopping in Japan would be. Anxious to buy something, anything, I settled on a punk teddy bear, made of what appeared to be deconstructed nylon socks and rudely pierced with a collection of nails. He was charming in a disturbing sort of way; he seemed very  Japanese; and his price, about $74, made him just the sort of souvenir I was looking for.

At least, that's what I thought. About a month later I got the shock of my life. Casually opening bills in my kitchen, I saw that Teddy had cost not $74, but $740! Alas, a mistake had been made—jet lag coupled with extremely poor math skills had caused me to misplace a decimal.

It took me a while to get over that disaster. When I told people about it they laughed, but with a little prodding they confessed to remarkably similar stories: the young starlet who bought $100 worth of tea in Indonesia, thinking she was spending $10; my own father, who many decades before had purchased an ice cream in Florence for $15, not $1.50 ("I was a millionaire for one day—in lire!" he liked to joke, back in the era before the euro.)

But it isn't only currency confusion that can lead to trouble. In fact, the more I probed, the more I came to realize that shopping while traveling resembles a high-stakes casino game—not only because this ostensibly pleasurable activity produces serious angst but also because there are actual odds involved: you have a one-in-three chance of buying something you love. The other two outcomes—you buy it and it's not quite right, or you resist temptation and subsequently pine away for it for the rest of your shopping days—are, sad to say, far too common.

Actually, there's a deeper reason why shopping on trips is so fraught: when you're on foreign soil, you really do feel like another person—more cosmopolitan, perhaps, or earthier, or more sophisticated, or more spiritual. Of course, that's the whole point of travel: to step outside ourselves and view the world through a wider lens than our everyday lives allow. In the glow of this enhanced perspective, we snap up items that suit our new personalities, only to find upon returning home that the sophisticated, spiritual person has vanished, replaced by the same old us, only now, as in the case of my friend B., freshly possessed of a pair of what we shall politely call bloomer-shorts.

B., a fashion executive too mortified to let us reveal her name here, bought this hybrid garment (plain, perfectly reasonable shorts with ruffled bloomers peeking saggily from the hems) on the Rue du Faubourg St.-Honoré, at Colette, a shop whose seductive spell—on my last visit Karl Lagerfeld was sitting quietly in one corner riffling through T-shirts—has caused shopping meltdowns in women far stronger than B. She went for the bloomer-shorts because, she says sadly, she thought they would look "so avant-garde, so cute with heels," but once home, they immediately joined the purple-leather Dolce & Gabbana pantsuit she purchased a few years before in Milan (in that fantasy, B. was a Donatella-ish blonde with attitude, not the soigné, raven-haired professional she is in real life), hanging dolefully in the never-worn-even-once section of the closet.

I have had similar experiences myself. In a tiny, enchanting shop near the Trevi Fountain, the specialty was carefully pleated, knee-skimming wool skirts. So convinced was I that such a garment, accompanied by a white shirt rakishly unbuttoned, tousled hair, high heels, and knee-socks, would give me a naughty schoolgirl allure, I bought not one, but two of these impossibly dowdy items. As soon as I got back to New York, reality hit: I have a Buster Brown bob and I can barely stand up, let alone cross a room, in high heels.

Lest you think these fashion faux pas afflict only women, rest assured that travel-shopping regrets are gender-blind. Antique jewelry dealer Ronald Kawitzky, a man brave enough to lend his name to this account, is still wondering why those red shoes he bought in Rome on the Via Condotti—a short walk from my pleated-skirt store—couldn't make the stylistic leap across the Atlantic. Everyone he saw in Italy was wearing goofy sneakers—yellow, peach pink—and he wore his new trainers for the rest of the trip, feeling like Marcello Mastroianni, like the kind of guy who has a closet full of candy-colored cashmere and drives a Lamborghini. And now?"I wore them once or twice in New York," he says with a trace of bitterness, "and everybody gave me really funny looks."

His story reminds me of my pal K.'s adventures in Barcelona. She waited outside the famous espadrille store in the Barri Gòtic until it reopened after the city's interminable lunch hour, took a number, and when she was finally waited on, spent hours deciding between wedge and flat, beribboned and slip-on, pale and bright. But even though Salvador Dalí himself used to order these shoes from this very shop, when K.'s trip was over she remembered that in summer she always wears Prada sandals to work and flip-flops when she's off duty. Her espadrilles—all six pairs—have suffered the same fate as Ronnie's scarlet sneakers.

But if they hadn't bought those ill-fated shoes, would they be longing for them right now?Victoria Ashley, the director of communications at Celine, still thinks about the frankly fake giant-pearl necklace she encountered years ago in London. She balked then at its high drama but has wanted to retrace her steps ever since. On the other hand, she did buy a safari jacket in South Africa—suede with some kind of furry lining—and while she adored her jacket in Africa, has it ever been worn for a shopping safari down Fifth Avenue?

And then there was the Grecian-style dress, purchased in Melbourne. "The few times I've worn it, I felt like I was channeling the days of ancient disco rather than ancient Greece," Ashley recounts mournfully.

Often it's not ourselves but our homes that are the unhappy recipients of misguided travel-shopping enthusiasm. A woman I used to know well visited China when that country first opened up to tourism. She fell madly in love with a patterned pink rug and wanted it for her capacious living room. Trouble was, she didn't know the exact dimensions of her salon. Her husband tried to stop her, but it was too late. She bought the carpet in what she thought was the right size, but it turned out her parlor was not quite as grand as she imagined. For years afterward the rug graced the room with one end rolled up behind the furniture, a rare disharmonious note in an otherwise immaculately decorated abode.

But as bad as these debacles can be, it's important to remember how life-changing travel shopping can be. Many years ago, in Europe as a college student attending a socialist rally (at the time, this was my idea of fun on summer vacation), I was stunned by the gorgeous women all around me. Back home, being a lefty meant overalls and Frye boots, but here you could man the barricades looking like Juliette Gréco in a silk dress and scarlet lipstick and patent pumps. I buried my jeans in the bottom of my suitcase, went to Galeries Lafayette, bought a Cacharel dress, and wore it practically every day for the remainder of the trip.

When I got home, I tossed my jeans in the garbage. And I've been dressing up ever since.

Lynn Yaeger is a Travel + Leisure contributing editor.