This summer, my boyfriend and I joined two other couples for a river cruise down the Danube. I was thrilled to visit parts of Germany, Austria and Hungary, places I’d never been before—places I never dreamed of when young. I was in awe of the lush green landscape, old castles, colorful small towns, and bustling cities. The most significant moment though, happened in our touring clothes: he in his awful gym sweat shorts and hiking boots, and me in tennis shoes and nothing special.

The moment I’ll always remember didn’t happen during our whirlwind tours through Nuremberg, Regensburg, Passau, Krems, Vienna, and Budapest...