Blake Lively Interview Magazine coverAlthough Blake Lively plays a confident, Upper East Side princess on 'Gossip Girl,' the actress has a difficult time opening up to people in real life.

"I'm actually a very shy person -- that's a big secret, so don't tell," Lively admits to Ben Affleck in September's Interview magazine.

"But being in [acting] classes pushed me to break out of that a little bit. It's like nature versus nurture: I'm naturally very shy, but I was brought up in a way where I had to get up and get out of that."

But those fears seem to be in the past for the 23-year-old blonde, who reveals she had to film a sex scene with Affleck on her very first day of shooting their new movie, 'The Town.' Yeow!