Virginia Madsen is hanging out on a farm in Santa Fe, New Mexico, with Billy Bob Thornton. They're working on a sweet little movie called The Astronaut Farmer, about a guy who builds a rocket ship in his barn. Madsen can't even talk about the film without smiling. "The location is so beautiful, and we sit around fires every night — it's like being at actors' camp." As for Billy Bob's bad-boy image, Madsen describes him as "surprisingly cuddly." Another hunk the 42-year-old actress has been working with lately is action-man Harrison Ford, her costar in the suspense thriller Firewall. "I didn't take the role so that I could be in a big-budget movie with Harrison," Madsen says. "I took it because I play his partner — not some damsel in distress — and I get to kick ass."

That in-your-face side is at the other end of the spectrum from her 2004 Oscar-nominated role as the wise, warm, wine-loving Maya in Sideways. Her real persona falls somewhere in between. It was toughness — and the help of an exceptional trainer — that enabled Madsen to bounce back after becoming depressed and unhealthy following the 1994 birth of her son, Jack (now 12), and subsequent breakup with his father, actor Antonio Sabato Jr. But it's her easygoing charm that shines through first and makes you want to get to know her. We caught up with her on a sunny Monday afternoon to talk about how she navigated the rough spots in her life and wound up happier than ever.

After appearing in 50 films, what was it like to finally get an Oscar nomination for Sideways?
Other actors who have gone through it will tell you that the awards season can be draining. But I had so much fun because I'd waited so long for it to happen. I realized that it would all be over soon and it would never happen again quite like this. Maya, the character I played in Sideways, was so embraced. There was no negativity, nothing to combat. And I was so ready for it. I had worked for years to have my mind and body in shape, but I was really, really strong when it came around.

Were you recovering from something specific?
I was not well after the baby was born. I just didn't recover quickly. And then, being a single mom, I got sloppy and didn't take care of myself. I became more and more depressed. I didn't know how to get out of it. So Antonio sent me to his trainer, Joe Sanceri, who is 73 years old. We don't just sit around talking. It's not therapy; it's a workout. When Antonio first suggested that I go see Joe, I could barely walk around without being in pain. I had become so sedentary that I'd gotten clumsy and weak. I would twist an ankle or hurt my back, and I suffered from terrible migraines. But Antonio told me that Joe could help. And he's become one of the greatest teachers I've ever known.

What were some of the things he taught you?
Joe taught me about my body and how muscles work. He made it exciting to go to the gym. None of my friends thought it would last, but he made it interesting. And 6 years later, I still work out. He taught me how to eat to make myself stronger, how to detox from all the bad food I'd been eating, and how to sleep better.

How did you stick with it?
I gave myself long-term goals: 3 months to feel better, 1 years to feel remarkably different. And I never made losing weight a goal. We took baby steps and one thing led to another. Working out led to eating better, which led to sleeping better. I wasn't so depressed. I had much more patience with my son. I wasn't so angry anymore. And that was the key because I have always been so hard on myself. If someone was treating me like I was treating myself, I would have divorced them.

Now that you've experienced the benefits, has exercise gotten easier?
I've never been athletic. It just doesn't come naturally to me. So I still have to work hard to make it happen. For me, getting myself to turn off the TV and leave the house, drive to the gym, and walk in the door is the hardest part of my journey. But I do it because I know how important it is for me to stay healthy.

What was it like doing the stunts in Firewall?
It was great, but I wasn't as tough as I thought. In one scene, which ended up being cut, I had to fall down a flight of stairs. Eventually I was thrown around so much that I ended up hurting my neck and covered in bruises. So I walked up to the director to tell him that I probably shouldn't do any more, and I heard a big crash — and here comes Harrison, who's 61 or something, diving through a window. Then he stood up as if it was nothing and was like, "How ya doing, Virginia."

Was working with him intimidating?
He's so masculine, but he wasn't at all intimidating. He was as approachable as a carpenter — but a carpenter with power. And that was really appealing.

What sacrifices have you had to make as a single mom?
I feel like one of those people spinning six plates at a time — I try to keep all the plates spinning. But really, I don't think there's any way to do both things completely successfully; because if I'm working and having this incredible time on this movie, I miss my son really badly. And if I'm home, I concentrate totally on him and my work life suffers. We drive ourselves very hard as women, and we have this idea that we can have it all. But we can't have it all at one time. We can have various things at different times. You have to choose what's most important at the time, even if that means that you sacrifice other things.

How are you managing now that work is taking center stage?
I chose to spend the first 10 years of my son's life with him. Now that I'm having my great year working, Antonio — a good friend and parental partner — is a stay-at-home dad. They're both very supportive of what I'm doing. I'm cool being in the limelight because I have my feet on the ground and my personal life is in shape. Now I can just get on the ride and go.

How Virginia Got Her Groove Back

Her Gym Angel City Fitness in Marina del Rey, California
Her Trainer Joe Sanceri

Her Routine
Weight training with supersets twice a week. "Supersets are working opposing muscle groups, doing back-to-back sets without breaks in between. Bodybuilders do these. For instance you would work a chest machine and then a back machine. By working this way you also get a cardio workout because your heart rate goes up and you maintain the pace throughout your time at the gym." Madsen also takes spinning classes and goes on hikes with her son and their dogs.

Her Biggest Challenge
Lower body. "After the weights we do a series of squats. I do so many of these that I can't even count them. I also do a calf workout! I call these exercises the devil chasers. It seems that I hold a lot of tension in my legs, and after the squats I do calf raises, and I can feel my brain open up ... really! It makes you let go of a lot of pain and think more clearly. It's the hardest job of all for your heart to pump down to the lower extremities, so when you force that, your body responds with loads of endorphins ... a great rush of happiness."

Her Abs Strategy
Switch it up. "I do three or four different kinds of situps. That way I don't get bored, but I do get plenty sore! But it's good to feel sore. You feel like you've accomplished something."

Her Fitness Advice
Go easy on yourself. "It's really easy for women to be down on themselves. You think: I failed again and ate pizza. So what? Then go for a bike ride. Just adjust. And realize that sometimes what you're craving is just what your body needs."