The cover of Bitney Spears' latest album "Circus".

Britney Spears admits her marriage to Kevin Federline was a mistake.

In her new 90-minute MTV documentary, "Britney: For The Record", the pop star talks candidly about her three-year marriage to Federline.

"I think I married for the wrong reasons," Britney said. "Instead of following my heart and doing what made me really happy, I just did it for the sake of the idea of everything."

The clip of the new show, scheduled to air on MTV on November 30, was posted on Sky1.com, a site for a British TV channel.

In the clip, as Britney talks about Kevin, her single "Womanizer" plays in the background.

"Your music is a reflection of what you're going through. It's such a part of me, the record, because of what I've gone through", she added.

In additional excerpts from the documentary posted by U.K.'s The Sun, Britney admitted to struggling with the restraints put on her life over the past year.

"There's no excitement, there's no passion. I have really good days, and then I have bad days", Britney said.

She even went as far as to say living under the control of others (her father Jamie maintains his conservatorship over Britney) is worse than being locked up.

"Even when you go to jail, you know there's the time when you're gonna get out. But in this situation, it's never ending. It's just like 'Groundhog Day' every day," she continued. "If I wasn't under the restraints I'm under, I'd feel so liberated. When I tell them the way I feel, it's like they hear but they're really not listening."

And while she had her fair share of personal problems over the last few years, Britney suggests she has changed her ways and learned from her mistakes.

"I never wanted to become one of those prisoner people. I always wanted to feel free," she said. "I think I've learned my lesson now and enough is enough."

(China Daily/Agencies November 22, 2008)