Find out how Jennifer Aniston got bikini-ready for her sexy Bora Bora vacation with her fiance Justin Theroux, according to her yoga instructor Mandy Ingber. Credit: George Pimentel/WireImage

Look who gets an "A" for self control! Jennifer Aniston's yoga instructor Mandy Ingber spoke to ABC News on Monday, Aug. 18, about how the star prepared for her most recent vacation getaway to Bora Bora with her fiance Justin Theroux.

"Jen's a very consistent exerciser and eater," Ingber said of the star's ability to maintain her flawless, bikini-ready physique at 45. "But when she has something she needs to focus a little more on, she just tightens it up a little bit."

Aniston, in fact, cut back on certain guilty pleasures ahead of her two-year engagement anniversary / Theroux birthday trip with her hunky beau. "She won't have the extra chips," Ingber explained of Aniston's self-control. "It's kind of like just being disciplined, she's like anyone else that she goes through those times when she can lose a little but pretty much, she's always in great shape."

As reported by Us Weekly, Aniston whisked her fiance away to Bora Bora for a romantic weeklong getaway to celebrate Theroux's 43rd birthday on Aug. 10 (Theroux also proposed to his love on his birthday in NYC back in 2012). "It wasn't a surprise, but Jen planned the whole thing," a source told Us of the stars, who spent their time in a bungalow at the Four Seasons in French Polynesia.

Aniston, who has been training with Ingber since the early '90s, is the type of person to exceed expectations, her trainer told ABC News. "She's an incredibly inspiring woman," Ingber gushed of her client. "An incredibly positive person, it's so obvious, everyone that works around her is doing really well, it's a lot because of her positivity is very contagious."

The star's personal life and wellness advice, it turns out, has also been a big influence on Ingber's life. "Jen is definitely somebody that has encouraged me to hydrate, she is a hydrator from way back in the day," Ingber said of the SmartWater spokesperson. "That's definitely one of the tips I use because I have so much more energy when I drink. When you stay hydrated, you’re not as hungry. Sometimes when you think you're hungry, you're actually thirsty."

As for how many downward dogs it takes to achieve Aniston's insane physique?

"We up the cardio a little bit, if she's looking to sort of trim down," Ingber said of Aniston. "So we add a little more cardio to the yoga, but also what she puts into her body is essential. That really is 80 percent of it ... it's not a big deal if you have a bite of this or that if you are mostly eating well."