Here's Michelle Obama's advice for couples this Valentine's Day: laugh with your partner.

She says it's what she and President Barack Obama do, and it seems to be working. Their marriage, although tested throughout the years by his political ambitions — for the Illinois Senate, the U.S. Senate and later president — is going on 19 years.

"I think a lot of laughing," the first lady said Tuesday at a White House luncheon with reporters who asked about the Obamas' union. "I think in our house we don't take ourselves too seriously, and laughter is the best form of unity, I think, in a marriage.

"So we still find ways to have fun together, and a lot of it is private and personal. But we keep each other smiling and that's good," she added.

It also helps that Obama is "very romantic."

"He remembers dates, birthdays," Mrs. Obama said last week on "Live! With Regis and Kelly. "He doesn't forget a thing, even when I think he is. . I'll have a little attitude. I give him a little attitude, but he always comes through."