Jennifer Aniston may be one of the most gorgeous stars in Hollywood, but she was still humbled and "very, very flattered" when she first heard the news that she was being named the Most Beautiful Woman in the World. "I thought, 'Oh my God,' " she tells PEOPLE in this week's cover story. "There was this sort of very excited, teenage-y kind of moment."
The actress, who says she's learned to embrace her appearance over the years, insists she feels her best when she's healthy and strong.
"It's funny, it's a really quick transition from not a care and now all of a sudden, we've got to really be mindful of what we put inside our bodies," she adds. "And how we sleep and take care of ourselves. You can get away with a lot in your 20s."
For more of Aniston's revealing interview, including beauty tips and secrets she's learned over the years, pick up this week's issue of PEOPLE on newsstands Friday
Aniston, 47, was first motivated to start taking care of herself early on in her career after an agent told her she didn't get a part because she was "too chubby."
"I was like, 'What?!' But my diet was terrible," she says. "Milk shakes and French fries with gravy [laughs]. It was a good thing to start paying attention."
Now the actress mixes it up by exercising at least six days a week for about an hour each day and watching her diet. But that doesn't mean she won't indulge in her favorites. From chips and guacamole to her husband Justin Theroux's pasta carbonara, which they make together every couple of weeks, "I'm not as strict as I was," she says. "It was always sort of a monitored watch. Then I thought just give yourself moderation."
Besides cooking and exercising with her husband, Aniston says just being married to Theroux brings her the greatest joy. "He makes me laugh. He's so interesting and so interested," she says. "He's unbelievably talented in more areas than one and he's just a good man."
As for her natural look, the actress gives full credit to her glam squad for teaching her "everything that I know! Whatever was happening before was just unfortunate," says the star, adding that she now knows how to contour her cheeks and blow out her hair. "When I was in my 20s, my face was almost a complete circle. So I really needed contouring. And now I'm slowly chiseling away, wishing I had that round face back."
If she could magically try any new look and instantly go back, Aniston says she'd be game to check out a pixie cut. "If I knew I could instantly push it back. I'm very curious to see what I would look like with really short hair," she says. "But I'll never do it. Never. I'm a long hair girl. It's like a security blanket."
So how does Aniston define beauty? "Inner confidence. Peace. Kindness. Honesty. A life well-lived," she says. "Taking on challenges and not feeling shame for things that haven't gone the way you felt they should have. And not feeling like a failure or allowing people to critique your life and make you feel like you've failed at something. That's just toxic noise."