For 34-year-old Canadian man Sandy Crocker, a dentist in British Columbia, that moment happened while he was on vacation in Ireland last year.
It sounds like something out of a romantic comedy: Crocker was smitten with the beautiful Irish lass, whom he saw across a cafe in County Clare while on vacationing with his family.
Crocker told the BBC that he only exchanged a few words with the woman ("the most beautiful Irish girl you could ever imagine," with red hair and freckles, of course) because he didn't want to be too forward.
"I watched her," he said. "She was one of those people who seemed the most genuine caring person you'd ever meet. I stood up and asked for directions and asked for the time - if I had just paid her a compliment, told her she was amazing, I could have put this to rest."
"She was eating and I didn't want to interrupt her meal so I waited until she was leaving and I asked her for directions to the Cliffs of Moher," he told Irish Central. "I was leaving Ireland a day later so, at first, I didn't see the point in pursuing things -- but after she left I decided I had to.”
Now Crocker is determined to find his mystery girl, more than a year after their fleeting moment together. He's given himself four weeks in Ireland in the hopes of tracking her down.
“I went back to work and my life, but there was always a joke here or there from my brother about the Irish girl in Ennistymon," he said. “She never left my mind, so I decided why not go back and try to find her.”
So far, Crocker has had a lot of fun, but not too much luck in his quest. In an email to TIME, he made light of the whole thing.
“Right now I’ve done the most I can and it truly, in the end, will come down to fate,” Crocker said. “I am prepared that she or I may not be right for each other, but I have gone to great lengths to find that answer.”
Crocker describes the dream girl as mid-to-late 20s, with reddish-brown hair and freckles. According to Clare People, Crocker had set up a profile on a dating site for the woman to contact him, but it appears to be closed.