The 26-year-old singer, who had two children with Federline, wishes she had never married her former dancer, reports FemaleFirst.
In a promotional video for her documentary, Britney: For the Record, the star said, "I think I married for the wrong reasons. Instead of following my heart and doing what made me really happy, I just did it for the sake of the idea of everything."
She added that her split with Federline influenced her music.
Spears and Federline were married in September 2004 and separated in the summer of 2006.