Jessica Biel says marriage to Justin Timberlake works because they're both 'selfish'

— -- Justin Timberlake and Jessica Biel have been together since 2007, and married since 2012.

How does the couple make their marriage work when both have such busy careers?

According to Biel, it's because she and Justin have a lot of the same values ... including selfishness.

"We believe in loyalty, honesty. We like to have fun. We like a lot of the same things," she told told Marie Claire. "Also, in the business, we're all very career-oriented, and you have to be a little selfish. I understand that about my peers -- about being focused and driven -- and if you can find that and someone who shares the same values as you, it's like: Score!"

Timberlake, 36, and Biel, 35, have a son, Silas, 2. Biel said that selfishness is sometimes hard to reconcile with parenting.

"You think you're a selfless person, and then you realize you're not," she admitted. "These little people come around, and they require so much, and your schedule is really not your own, nor is it important anymore, and it's very clear that it's your life now revolving around this dude."

Timberlake will perform at two major music festivals in September, and in December, he'll be seen in the Woody Allen movie "Wonder Wheel." He'll also appear in "Trolls 2," and at some point, he'll release a new album. As for Biel, she stars in the new USA series "The Sinner."