Inside Jennifer Aniston's 'Perfectly Happy' Single Life Following Justin Theroux Split (Exclusive)

Jennifer Aniston is doing just fine following her split from Justin Theroux in February.

Jennifer Aniston is doing just fine following her split from Justin Theroux in February.

A source tells ET that the 49-year-old actress has been flourishing since the two decided to call it quits after two years of marriage. According to the source, Aniston and Theroux definitely don't regret the big decision to go their separate ways.

“Jennifer has been doing incredibly well," the source says. "Her decision to move forward in life without Justin was one of the most difficult of her life but she now knows for sure, it was the right one. Since they split, her friends believe their plan to move forward in life without one another was the best decision for both of them. Neither of them is pining for each other but instead, finding themselves again."

The source notes that the former Friends star "looks great," is currently in the best shape of her life and has taken time to focus on her health and her future.

"She has been on a new diet and has been eating mostly fruits and whole grains," the source shares. "She’s addicted to her egg whites still for maximum protein."

Aniston's career has also been thriving. Earlier this week, ET confirmed that Steve Carell is joining her and Reese Witherspoon's highly anticipated Apple TV show about morning television shows. Aniston and Witherspoon are also executive producing the project with their respective production companies, Echo Films and Hello Sunshine.

“Her career has always been important and that hasn’t changed since the split," the source says. "She has been working nonstop, she has a new project with Steve Carell and everybody’s expecting it to do really well. She’s surrounded herself with close friends and feels more centered than ever because she’s not dating anyone and she’s perfectly happy."

As for the actress' relationship with Theroux, the source says, not surprisingly, the two aren't as close despite their decision to split being a mutual one.  

“Jennifer and Justin made a deal to stay in touch as much as possible but that hasn’t been easy," the source says. "The communication between them has taken a back seat. They were truly best friends."

Interestingly enough, in March, a source told ET that 47-year-old Theroux was also focusing heavily on his fitness following his breakup from Aniston, becoming "more committed to a consistent regime" and working toward "his revenge bod." The actor has indeed been snapped frequently by paparazzi out and about post-workout. 

"Justin has been hitting the gym hard since the split," the source said at the time. "He's been working out for over an hour every day at Gotham Gym. Boxing is a big part of his workout routine." 

Last month, Theroux opened up about their split for the first time and stressed that he and Aniston are still on good terms.

“The good news is that was probably the most -- I’m choosing my words really carefully -- it was kind of the most gentle separation, in that there was no animosity,” he told The New York Times. “In a weird way, just sort of navigating the inevitable perception of it is the exhausting part.”

“It was heartbreaking only in the sense that the friendship would not be the same, as far as just the day to day," he added. "But the friendship is shifting and changing, you know, so that part is something that we’re both very proud of.”

Meanwhile, in Aniston's first major interview since the split for InStyle's September issue, she also stressed she wasn't "heartbroken" over the breakup and showed off her toned physique in the accompanying photo shoot.

"It’s pretty crazy. The misconceptions are 'Jen can’t keep a man,' ... Or that I’m sad and heartbroken," Aniston said. "First, with all due respect, I’m not heartbroken."

"When a couple breaks up in Hollywood, it’s the woman who is scorned," she added. "The woman is left sad and alone. She’s the failure. F that. When was the last time you read about a divorced, childless man referred to as a spinster?"

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-- Reporting by Adriane Schwartz