As a lifelong traveler, I’ve made my share of money mistakes abroad — like tipping when it wasn’t expected (offending the tippee) or overpaying for sluggish WiFi for a patchy call back home. And I’ll never forget the one time I spent a fortune on gratuities while stuck at the Dar es Salaam International Airport in Tanzania because I had only large bills, not small coins, as I waited out a days-long delay.