The pair met "when [Theroux] was writing on 'Tropic Thunder .' We were just buddies, and then buddies through 'Wanderlust'  ... it's almost impossible to get bored with one another. We've tried so hard! And even that's interesting because his eyes are so pretty, but we can entertain ourselves and talk about endless things, which is pretty great," she told the magazine of the man she became engaged to in 2012.
But before they took the next step as an official couple, Aniston admits she had to figure some things out and stay single to do so.
"It really helped me get to a place where I was more comfortable with myself, truly ready for love and for a partner," she said. "The past wasn't 'less than.' It was extremely important to my growth as a woman. But if you take the law of attraction, if you only love yourself 70 percent, that's what's going to come back to you."
She continued, "So you fill up that 30 percent, then all of a sudden there's this pure, good love standing right in front of you. Then you realize, 'Oh, this can be easy! It doesn't have to be so hard.'"
"He's just been doing it so graciously and gracefully, and it's a strange ballpark to walk into. He's in his body, for sure. He's a pretty realized person," she said of "The Leftovers" star.
She continued to gush, "Not only is he a great actor but he's one of the best comedy writers out there. And he directs and paints murals. And I just think it's so attractive to be that good at so many things and to have no ego. He's one of the most humble, decent human beings.”
Finally, with so much going right for the "Cake" actress, Aniston, 45, said she's happier than she's ever been and enjoying life in her 40s.
"I've had more fun post-40 than I can remember," she said. "From a work point of view, a physical point of view, a psychotherapeutic point of view."
Harper’s BAZAAR’s December/January issue hits newsstands Nov. 25.