For Lana Condor and Noah Centineo, starring as Lara Jean Covey and Peter Kavitsky in Netflix's "To All the Boys," changed their lives.

It was Condor's first leading role ever and making the three-part franchise challenged the 23-year-old in ways she never expected. 

"I really learned about conserving your energy and the importance of not letting people take advantage of your energy and your time," she told Fox News while promoting the third film "To All the Boys: Always and Forever." 

"I do think there was a real moment when we like during a sequel that there was just so much happening and I was saying yes to everything because that's what we're taught to do, but then I like woke up one morning and realized I have literally nothing left to give. I'm completely depleted," she recalled. 

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For 24-year-old Centineo, walking away from the trilogy with life-long friendships changed his perspective about the film industry. 

"[I learned] how important it is to maintain a long term perspective on the relationships that you're forging and building throughout the course of your trilogy or TV show or whatever it is," he told Fox News. 

Lana Condor as Lara Jean Covey, Noah Centineo as Peter Kavinsky in 'To All the Boys: Always and Forever.'  (Katie Yu / Netflix © 2020)

"I remember when Lana and I came back for movie two it was the first time we had seen each other because she had been she'd been working nonstop in Vancouver. I believe we saw each other and we were like, 'What was it like for you? Like, what's going on? And we got to share. It was cool to have someone else that has experienced the exact same type of [things] as I had. I just think it's great to have that support system," he described. 

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Over the course of filming the franchise, Condor said she's most proud of Lara Jean's growth. "She's grounded more. I think she's stepping out into the world in a more confident way than what we started with," she explained.

Noah Centineo as Peter Kavinsky, Lana Condor as Lara Jean Covey, Ross Butler as Trevor, Madeline Arthur as Chris.  (Katie Yu / Netflix © 2020)

"I think in the beginning part of her charm is that she lives in her head. She lives in books. She doesn't really put herself out there. So it's a journey of watching this girl whose natural instinct is not to leap. We're watching her now just kind of slowly jumping. Her confidence has grown," she added. 

Centineo said it was exciting on this third film to explore the more vulnerable part of his character. 

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"I thought it was always necessary to explore that side of Peter. It makes him more than just, you know, a really positive force. It shows a little bit of the shadowy side of Peter," he said. "I think he's got a lot of personal demons that come to a resolution in the third film."

"To All the Boys: Always and Forever" premieres Feb. 12 on Netflix. 

Fox News' Liza Aristizabal contributed to this report.