Any argument, she says, exhausts her. "I'm the one who wants to talk about it calmly and try to learn from it and move forward," says the actress, 31. "I walk the walk, not talk the talk."

The My Name Is Earl star gets to play a more tempestuous version of herself in the buddy comedy I Love You, Man, opening Friday. When Pressly's hilariously forthright Denise isn't bickering with her husband (Jon Favreau), she serves as the sounding board for friend Zoe (Rashida Jones) when she gets engaged to friendless Peter (Paul Rudd).

Man director John Hamburg calls Pressly "a fierce woman, and I mean that in a great way. But she's a lot nicer than Denise, who's really nice to the people she likes but not so nice to her husband. (Pressly) is super-funny and just kind of no-nonsense."

Like Denise, Pressly has a core group of confidantes. "I've had the same best friend since I was 5. There are six of us girls from high school who have been friends for the last 16 years. We were just together last weekend. We've all had boys. All of us are single except one."

Son Dezi is almost 2, and she and Dezi's dad, DJ Eric Cubiche, split up in November. Pressly isn't tearing up the dating scene quite yet. "It's still fresh, the separation. I've just got to focus on Dez."

Her son, in fact, inspired Pressly's book, It's Not Necessarily Not the Truth: Dreaming Bigger Than the Town You're From, out Tuesday. Pressly, a native of Kinston, N.C., has been on her own since 15 and says the book is simply different stories about pivotal people and events that helped her get where she is today.

"When I found out I was pregnant, I started writing it, and I was writing just for my son," she says. "And then my girlfriend helped me put the book together and get it done."

Pressly is not self-important enough to write her life story while still so young. "It's not by any means my 31-year-old autobiography. I'll do another one in three years," she jokes.

It's not as if she doesn't have material, including her success in Earl (NBC, 8 p.m. ET/PT Thursdays). In 2007, she won a supporting-actress Emmy for playing Earl's opportunistic ex-wife, Joy.

With the show in its fourth season, she says, "I don't get bored, I don't get tired, I love every second of it. It's really cool to play her because she's deeply disturbed, yes, but there has been a lot of heart put back into her. We've made her more human."

Sometimes, Pressly takes Dezi to the Earl set. She has worked out her schedule, so she either wakes up with him and gives him breakfast or puts him to bed. Her son's infanthood "has gone so quickly," she says, snapping her fingers. "It's gnarly. I remember being pregnant like yesterday. He came out like Superman. It was so cute."

As Pressly digs into a bowl of macaroni and cheese, it's hard to believe that the trim and tiny woman gained 42 pounds during her pregnancy, ultimately weighing 156 pounds. Pressly says she was "ginormous" at the time.

Ten days after giving birth, she went back to the gym. "I worked out so hard. I started doing two hours a day, six days a week," she says. "Two and a half months after he was born, I was turning 30, and the last thing I wanted to do was be fat at my 30th birthday party in Vegas."