"I want them to understand how it happens," Remini tells ABC News' Dan Harris in an upcoming interview

In a first look from Leah Remini‘s upcoming 20/20 interview about her new tell-all book – Troublemaker: Surviving Hollywood and Scientology – the actress opened up about the controversial church and why she left.

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The former The King of Queens star, who publicly broke ties with Scientology in 2013 after years of membership, told ABC News that she wants people to get a look at what life is like as a member of the religion.

“The decision to leave is your giving up everything you’ve worked for your whole life,” Remini, 45, said in the clip. “I feel that people need to understand this has been my whole life.”

The star said she wants her fans to “understand how it happens.”

“As time goes on, you start to lose touch with the real world. The mindset becomes us against them,” Remini said.

Former Scientologist Leah Remini Shows Support for Scientology Doc

The actress, who currently has her own reality series on TLC called Leah Remini: It’s All Relative, hasn’t been afraid to speak out against the church, which is the main subject of her book, due Nov. 3.

Remini has a 30-year association to Scientology and was initially brought into the religion by her mother.

“I don’t think people know the amount of dedication it takes to be in this organization,” she said during an interview earlier this year. “It was every day, three and a half hours minimum, seven days a week usually.”

The star’s own youth in the church (“We went from a middle-class lifestyle [in Brooklyn] to living in a roach-infested motel with six other girls off a freeway in Clearwater,” she once revealed) was what pushed her to leave – she didn’t want to subject her own daughter to the lifestyle.

“I decided I didn’t want to raise my daughter in the church because from what I’ve experienced and what I saw, the church becomes your everything,” she said on her reality show.

Church International Spokesperson Karin Pouw told PEOPLE in a statement that Remini’s claims are an effort to drum up attention for herself.

“It comes as no surprise that someone as self-absorbed as Leah Remini with an insatiable craving for attention would exploit her former faith as a publicity stunt by rewriting her history with it,” Pouw said, “including omitting that she was participating in a program to remain a Scientologist by her own choice, as she was on the verge of being expelled for her ethical lapses.”