Jennifer Westfeldt and Jon Hamm ''complement'' one another.
The couple have been together for 14 years and the actress believes the key to their relationship success is their strong friendship.
She said: ''I think we're very complementary. I tend to freak out and he's really mellow. He makes me breathe.
''In any long relationship you have to be best friends because life isn't always rosy. It's weathering the highs and lows together that is what real relationships are about.''
The couple also refuse to go more than two weeks without seeing one another, even if it means a gruelling round trip.
Jennifer explained to Grazia magazine: ''We have a two-week rule never to go without seeing each other and we've never broken it.
''Sometimes it means one of us gets on a plane for 18 hours and then turns around again - but it's worth it.''
Despite being together for so long, the couple have never married, and Jennifer insists it isn't important to them.
She said: ''Choosing each other every day is stronger than any piece of paper.
''Which is not to say we won't get married someday if we think of it, but it doesn't feel different or more legitimate than what we have. People get obsessed with weddings and often they're not about the couple but everything else. We would never want that.''