FORTUNE -- No one ever doubted that Jennifer Simonetti-Bryan, 37, was a type A personality. Growing up, she played first violin in the youth orchestra; later, she earned a brown belt in tae kwon do. After graduating from the University of Denver in 1995, she became a management associate for Citicorp (now Citigroup (C, Fortune 500)), where she worked in loan syndication and corporate finance.
But a few years later, Simonetti-Bryan had an existential crisis that many young professionals face: Working nights and weekends, staring at models on a computer screen, she felt bored and unsatisfied. Only 10 more years, a colleague told her, and she'd make managing director.
A few weeks after that, a fateful business lunch set the analyst on a new course. While giving a presentation in the corporate dining room of Citicorp's London office, Simonetti-Bryan was served an herb-crusted salmon paired with a Sancerre, a crisp white wine from France's Loire Valley. The way the acid in the wine cut right through the oil from the fish sparked her curiosity. She began taking classes in wine appreciation, and in the wake of Citi's merger with Smith Barney in 1998, she took the plunge, abandoning her six-figure salary for a wine shop job, then becoming brand manager for Cakebread Cellars and Domaine Carneros while collecting industry certifications.
One of those was the Master of Wine designation, the industry's highest honor. After passing a four-day exam that involves identifying 36 wines, applicants must write an original piece of research that furthers the industry. Simonetti-Bryan studied six hours daily on top of a full workday, sometimes suffering from "palate fatigue." "There were some days," she says, "where I was like, 'I don't want to look at a glass of wine. I don't even want to think about a glass of wine,' and then you get that one glass of wine and you go, 'Ah, this is why I'm doing this.'" In 2008 she became only the fourth woman in the U.S., and one of 289 people worldwide, to obtain the coveted title.
Today she travels the world as head of her company, JSB Consulting, educating and training others in the wine and spirits industry or conducting seminars for firms like UBS (UBS) and Morgan Stanley (MS, Fortune 500) -- the types of places she might be employed by if not for that fateful glass of Sancerre. She is an industry commentator and a judge for international wine competitions, as well as a professor for The Great Courses' Everyday Guide to Wine -- and she's truly happy. "If I had all the money in the world," she beams, "I would be doing exactly what I'm doing right now." Now that alone deserves a toast.