Leah Remini talks about why she left Scientology

It's not easy to quit something after 30 years, but Leah Remini did just that when she left Scientology.

The "King of Queens" star had grown up in the church since she was a child, and left in 2013. She said in an interview on "20/20" that Tom Cruise was one of the reasons why she left Scientology.

"Being critical of Tom Cruise is being critical of Scientology itself ... you are evil," she told correspondent Dan Harris.

In a promotional clip, Remini explained that her ties with the church ran deep.

"The decision to leave is your giving up everything you've worked for your whole life," she said. "I feel that people need to understand this has been my whole life."

"As time goes on, you start to lose touch with the real world. The mindset becomes 'Us against them,'" continued the actress. "The decision to leave is you are giving up everything you have ever known and everything you have worked for your whole life."

Remini is one of several stars who left Scientology. Filmmaker Paul Haggis spoke out against the controversial religion in the documentary "Going Clear."

The interview airs on ABC at 10 p.m. on Friday.