These days, the sober Demi Lovato is proud of her restraint from drugs and alcohol, but there was a time when the "Cool for the Summer" singer had a pronounced case of party-FOMO.

Lovato, who sports a diamond-mine dress on the September issue of Cosmopolitansays she used to be jealous of certain pop stars who made their revelry public, but ultimately learned staying clean was simply in her best interest.

"Miley—in her music video 'Can't Stop,' her whole thing was partying and not giving a f---," Lovato explained. "Part of me was super jealous that I couldn’t be like that. I had to look at my life and be like, 'Okay, that's just not what you can do. There's no need to be bitter about it.'"

Still, Lovato insisted she's no prude, and said that when it comes to her music, there's little she's unwilling to say.

"There are a lot of girls in pop—they have badass lyrics, but I feel like I’m the only person other than Rihanna and Nicki Minaj who isn't afraid to say, 'Try something on me and I'll f---ing beat your ass,'" Lovato said. "There are people who can dress up and play the part, but their music doesn't say it."

Pick up the next issue of Cosmopolitan for more, and tell us what you think of Demi's admission!