Britney learned a lot about herself , both on and off exercise set .

Britney Spearsis happy to have her acting days behind her, and now she’s sharing how a missed opportunity turned into a blessing in disguise.

As she prepares for the upcoming release of her memoir,The Woman in Me, Britney shared an exclusive excerpt from her book withPeopleabout auditioning forThe Notebookand why she’s thankful she put acting behind her.

In 2002, Britney debuted her first feature film,Crossroads, alongsideZoe Saldañaand Taryn Manning. But the pop star admitted that the experience wasn’t really easy for her.

“My problem wasn’t with anyone involved in the production but with what acting did to my mind,” Britney wrote in her book. “I think I started Method acting — only I didn’t know how to break out of my character.”

“I really became this other person. Some people do Method acting, but they’re usuallyaware of the fact that they’re doing it.But I didn’t have any separation at all.”

Britney said she ended up carrying herself different, talking different, and even walking different months after shooting the film. But those changes didn’t stop her from auditioning for more movies.

The “Stronger” singer also revealed she almost starred in the box office hitThe Notebookwith her formerMickey Mouse ClubcostarRyan Gosling, but the leading role ultimately went toRachel McAdams.

“That was pretty much the beginning and end of my acting career, and I was relieved.The Notebookcasting came down to me andRachel McAdams, and even though it would have been fun to reconnect withRyan Goslingafter our time onTheMickey Mouse Club,I’m glad I didn’t do it.”

“I imagine there are people in the acting field who have dealt with something like that, where they had trouble separating themselves from a character.”

Britney referred to acting as one “occupational hazard” she hopes she never gets close to again. It forced her to be half herself while also living half of her life as a fictional character. After a while, she wasn’t able to decipher what was real and what wasn’t.

Instead, Britney put her focus back into her music as she worked on her fourth studio albumIn the Zone. She was also dealing with abreakup— her highly publicized relationship withJustin Timberlake.

The album was released in the fall of 2003, and it was accompanied by several hit singles including “Toxic,” “Everytime,” “Outrageous,” and “Me Against the Music.”

To learn more about Britney, be sure to check out more excerpts from her book onPeopleor in her memoir,The Woman in Me, when it hits stores Oct. 24.

Closeup of Britney Spears

Closeup of Britney Spears

Screenshot from "Crossroads"

Screenshot from "Crossroads"

Screenshot from "Crossroads"

Closeup of Britney Spears

the cast of "The Mickey Mouse Club"

Screenshot from "The Notebook"

Screenshot from "The Notebook"

Britney onstage

Closeup of Justin Timberlake and Britney Spears

Britney Spears, Madonna, and Christina Aguilera onstage