Kelly Clarkson needs a refresher course on her own songs.

During a rehearsal on Friday, the 34-year-old singer went on Facebook live to sing a few of her hits for her fans, but couldn't seem to remember her own lyrics.

WATCH: Kelly Clarkson Sings Live for First Time After Going on Vocal Rest

She started her mini performance with "Catch My Breath," but flubbed the lyrics before admitting she wrote the song. Before singing "Beautiful Disaster," Clarkson asked for a line, and later had to immediately jump to the chorus of "Cry" because she couldn't remember all the words. "There's a lot of songs," Clarkson exclaimed. "It's been 15 years."

Whenever she couldn't recall a word in the song, Clarkson would replace it with "something." The mother of two nearly got through "Already Gone" before she flubbed. "I'm going to get so much crap for this!" she quipped. "This is the worst idea."

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"Walk Away" started out well, but she forgot the second line. "Dear Lord, I don't know lyrics!" she said. "This is hard! I'm sweating!"

For her last song, Clarkson sang "A Moment Like This," which was the song she performed after winning American Idol in 2002 -- but again, she couldn't remember all the words. "You're welcome for the comedy hour," Clarkson joked. "Sorry I didn't know my lyrics."

Looks like rehearsal is necessary.

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ET has been with Clarkson since the start of career. "What I want to achieve is, I want longevity," she shared in 2002 when she was just 20. "I want to be able to reach different crowds, different ages. I want to be the type of performer that people, you know, backstage I can actually sit there and talk to them. I want to take time out."

Clarkson has clearly surpassed her goal, with too many hit songs for even her to remember.

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