In The Ugly Truth, Katherine Heigl plays a woman who is clueless in the ways of romance. But in real life, the actress considers herself fairly savvy on the subject.

"In my early 20s, I didn't know who I was or what I wanted," the 30-year-old Grey's Anatomy actress tells InStyle in its new August issue, "and if you're just getting to know yourself while you're in a serious relationship – it's like you're trying on different personalities."

"You try to see what fits, but there is that real you in there somewhere."

Katherine Heigl says she finally found her real self when she met singer Josh Kelley, her husband of 18 months, on the set of his 2005 music video for "Only You."

"I was fed up with trying to be somebody else, and got really lucky and met a great guy who loved me for me," the Emmy Award-winner told the magazine.

Heigl, who it appears will be back for Season 6 of Grey's Anatomy despite a year's worth of rumors to the contrary, says her experiences have not only helped her learn what she wants in romance but also what she wants in a movie – and she says it isn't rated PG-13.

In a real relationship, Heigl opines, "you're probably going to drop the F-bomb once in a while. You're probably going to say some things that are kind of harsh."

"And you're definitely going to talk about sex. It doesn't have to be so Snow White and Prince Charming. That's my problem with a lot of romantic comedies."

It's that sass and forthrightness that The Ugly Truth costar Gerard Butler says made him fall madly in love with her after watching her 2007 hit Knocked Up.

"This is the sexiest, smartest, sassiest, funniest actress out there," he said. "And suddenly you get told they want you to read a script with her? I love this business!"

Click to enlarge more Katherine Heigl pictures from InStyle ...

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.