Speaking at the Fortune Most Powerful Women “Evening With…” dinner in Washington, D.C. on Wednesday evening, Valerie Jarrett, senior advisor to President Barack Obama, shared the fortuitous story of how she and Obama met: At a dinner, where Jarrett was trying to convince his then-fiancée to come work for her.

At the time, Jarrett was deputy chief of staff for Chicago Mayor Richard Daley. And that fiancée? Her name was Michelle Robinson—now First Lady Michelle Obama.

Jarrett, a former lawyer, bonded with the future Mrs. Obama about their mutual distaste for working in Big Law. “I would sit in my office and just cry,” Jarrett said of the early days of her law career.

Yet convincing Michelle meant convincing her beau, who “didn’t think [the job] was such a great idea,” recalls Jarrett. So a dinner was arranged and Jarrett inadvertently met the future President of the United States. “Wow, am I glad I said yes!” she told the audience of her decision to agree to have dinner with the couple.

Sign up: Click here to subscribe to the Broadsheet, Fortune’s daily newsletter on the world’s most powerful women.

While Jarrett eventually convinced Michelle to join her at the mayor’s office, the two women’s roles were reversed just a few years later. Obama had just been elected president, leaving Jarrett with two options: Join him in the White House or run for his now-vacant Illinois Senate seat.

Now, it was Michelle Obama’s turn to convince her former boss to take a job. “Why on earth would you want to be in the Senate?”Jarrett recalls Obama asking her. And if you think the President is good at getting what he wants, says Jarret, “he’s nothing compared to the First Lady.”

Jarrett ultimately agreed and spent the past eight years serving in the Obama administration. Formally, she has been the President’s assistant for public engagement and intergovernmental affairs. Informally, she has also been one of his closest advisors and confidantes.

“She is one of our best friends, somebody who is practically a sister,” the President said of Jarrett in an interview with the Wall Street Journal.

The D.C. dinner is the kickoff event for the annual Fortune/U.S. State Department Global Women’s Mentoring Partnership, a three-week program that pairs women from emerging markets with senior female executives from companies such as The Dow Chemical Company, Accenture, and Johnson & Johnson.

Jarrett’s story left the mentees—and the rest of the crowd—with a valuable lesson: Think twice before you say ‘no’ to the next dinner invitation.