Valentine's Day advice from Michelle Obama: Laugh!

But just to reinforce the image, the first lady revealed the secret of the success of their 18-year-marriage: 'A lot of laughing.'

Her comments came just in time for Valentine's Day on Monday.

She told reporters at lunch over the weekend that she and the president laugh a lot, and it seems to work, despite the stresses of life in the White House, according to media reports.

'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. We still find ways to have fun,' she was quoted as saying.

'A lot of it is private and personal. But we keep each other smiling, and that's good.'

She said that the president is 'very romantic.'

'Got to keep the romance alive, even in the White House,' she said.