Yes, Winnie Cooper is 50. Danica McKellar on growing up, finding faith and leaving L.A. for Tennessee.

Danica McKellar will forever be known as Winnie Cooper. She didn't always love it.

The actress was 13 when The Wonder Years premiered, and almost overnight, she became the "generational dream girl" of late '80s and early '90s television. But McKellar says it was strange to experience fame as a teenager — she had to wear disguises to go out, and she struggled to figure out her identity outside of her onscreen alter ego.

"I needed to find out who else I was besides Winnie Cooper," the former teen star tells me in conversation for Yahoo's Unapologetically series.

After the series ended, McKellar stepped away from Hollywood and enrolled at UCLA, where she earned a degree in mathematics. While she eventually returned to acting, her love of math — and her mission to help kids — became her calling.

Over the past two decades, she's written 12 children's books about math , including the just published I Love You 100 . And leave it to McKellar to make the math work out just right: Her 12th holiday movie, Have We Met This Christmas? , which McKellar wrote, premieres Dec. 13 on Great American Family.

Now 50, McKellar credits Winnie for putting her on the right path. The role she played as a teen "has flavored and shaped my whole career" and helped her carve out a "wholesome" career path.

It's a path that has seen her relocate from Hollywood to Tennessee, where she's raising a teen of her own, 15-year-old son, Draco. Here she opens up about child stardom, her faith and what lessons she's learning at 50.

You have these two parallel careers: being an actress and a mathematician. Was there a particular moment when you realized that math could be part of your identity in addition to acting?

A few months after I finished The Wonder Years [in 1993], I went to college. I ended up taking a break from acting completely for four years to get a degree in mathematics. At one point, I thought I might become a mathematician, and I did work as a professional mathematician one summer, helping to prove a new theorem.

But what I found was, as much as I love the problem-solving and the challenge of math, I missed emoting and sharing stories with people. So I joined the Shakespeare group on campus and eventually returned to acting. But I never forgot my love of math, especially as I became aware of the insecurities that women, in particular, often have surrounding math. I wanted to get math some better PR and make it more accessible to kids. I thought I was only going to be writing one book, Math Doesn't Suck , [published in 2007], but now I have 12.

You have a new holiday movie coming up that you wrote. Talk about stepping into the creative role of writing this one.

I've always wanted to play the role of a woman who gets amnesia. In this movie, my character vowed never to speak to her ex again, but after a car accident, she wakes up at his family's inn with no memory. He has to pretend that he doesn't know her — the doctor said he couldn't do anything that upset her — and it's a second-chance-at-love story. It was a delight watching my words come to life.

You turned 50 this year. How are you feeling about this decade?

When I turned 40, I was like, "Oh, what does this mean?" But then my 40s were the best decade ever because I just stopped caring so much about what people thought. I just knew who I was. I knew what I wanted. I didn't have all the insecurities from my 20s and 30s. I've heard your 50s are even better. [It's] when you really stop caring what other people think and you really live for yourself and your own family and your own decisions. You're not trying to get the approval of other people.

How do you prioritize your wellness at 50?

I've always been active — dance, Pilates — but when you turn 50, especially as a woman, you need to start lifting weights. Not heavy weights, but you need to do resistance training. It becomes really important for your health.

At the end of my 40s, I noticed I was putting on a little bit of weight. I thought, That's odd , because I was doing all the same things I always did. But I realized our bodies need more now. We need to do extra. In talking to some personal trainers, I learned we need to lift some weights, so I've integrated that into my routine. I usually lift eight pounds.

How has your faith guided you when it comes to finding balance in your life?

My relationship with God is something I hadn't spent much time thinking about until three or four years ago, when I really started my faith journey. I've always been a worrier, and having this relationship with God has made the biggest difference. My life doesn't look that different from the outside [but] I have a sense of peace in not knowing what's going to happen in the future — just trusting God, trusting the process — which I didn't have before.

You moved from California to Tennessee in the last few years. What has that been like for your well-being?

I lived in California — Los Angeles, in particular — nearly my whole life. For the last three years, we've lived in Tennessee, and it's truly beautiful. It's fall now, and all the leaves are changing. I love the seasons. We actually even get snow in January. We have a hill in our backyard, so we get to go sledding. I will go sledding even when Draco's not here. When he's with his dad [ex-husband Mike Verta], I totally will still sled.

What is it like being the mom of a teenager?

My son's 15 years old. We're very close and always have been. I homeschool him, so that probably helps. We hang out. He's not like: "Mom, get away from me." ... He's taller than me now. He's 5'9" and I'm 5'4". He just keeps growing. It's wild to watch him transform into this man. He's not quite there yet, but he's getting there. It's a front seat to the best show in the world.

You became famous when you were so young, and people probably associate you with that age. How has that shaped the way you've navigated your career — always having Winnie Cooper in the background?

When I was a teenager, I became weary of always being recognized as Winnie Cooper on The Wonder Years . I went through a phase where I didn't want to be recognized. I'd put on a disguise before going out. It was so silly. For many years, I have realized what a gift it has been, and how it has flavored and shaped my entire career. Winnie Cooper was such a wholesome character. It was a wholesome show.

Now getting to do [Christmas] movies is so wholesome. It's putting positive energy into the world — and I love being able to do that. I also love that the nostalgia from The Wonder Years helps to color and flavor my Christmas movies now. When someone sees me in a movie, it's extra nostalgic and warm and fuzzy, which is great for a Christmas movie. It's just baked in because of Winnie Cooper, and I'm very grateful.

How do you feel when you watch your early roles?

I don't. I did try to show Draco The Wonder Years once when he was 12, but he had no interest. He didn't recognize me. He had no idea that it was me. He had no interest. I was just like, "That's fine. You don't have to like the show. You don't have to watch the show."

It was wild watching it after so long. I don't think I look the same, but people recognize me in the street and will say, "You look the same as you did before." I'm thinking I don't, but maybe because we all kind of grew up together? Twelve-year-old me and 50-year-old me look pretty different, but maybe if you were 12 when the show was on, and now you're 50, you see me as the same.

What's your relationship with social media like these days? I read that you don't bring your phone to bed.

Social media is a wonderful tool, and a fun way to stay in touch with people. It also has within it a time-suck trap, so you have to be careful. When I go on social media, I try to make sure that I have a goal and I'm not killing time. We have so many more conveniences in the world now, like buying our groceries and having them delivered, but if we spend that extra time scrolling, we haven't gained anything. We're just turning our brains to mush. So I never bring my phone into bed with me at night. In the morning, I will wake up to start answering emails, but not scroll. I'm teaching Draco too: "Look, when you get on your phone, if you find yourself scrolling, just know that that app wants you to scroll and waste your time and waste your life on it. Just keep that in mind, and don't let it beat you. Be deliberate, be intentional."

Looking ahead, what are your hopes, dreams and goals for this decade of your 50s?

My goodness, I'm so grateful for my life today — with my math books, my movies, getting to be involved as a producer — and I hope I get to keep doing that. Also I look forward to ushering Draco into adulthood this decade. He'll be 25 in 10 years. My hopes and dreams are that I can help to guide him so that he can embark on his 20s as confidently as possible. The 20s are such a decade of insecurities and self-doubt. I hope he can get around some of that.

This interview has been edited for length and clarity.