12/27/2013 at 02:00 PM EST
If Britney Spears
indulged in any holiday feasting this season, it certainly isn't showing.
In the wee hours of Friday morning, the pop singer Tweeted
a sexy photo of herself rehearsing for her new Las Vegas show
, "Piece of Me," opening Friday night.
"Can't believe the 1st show is almost here!!!" she says in the caption.
Fans got a behind-the-scenes glimpse of Spears prepping for her Vegas residency
in the E! documentary
, I Am Britney Jean
, in which the pop icon confessed to being a poor match for the entertainment business.
"I have always been kind of shy, since I was a little girl," she says
. "It's who I am to be modest, so I really can't help it. I turn into this different person … seriously, bipolar disorder … This is all I've know all my life – cameras, being followed, being part of the industry. … I'm not really made for this industry."
Spears also confessed to enjoying sex, but to having a new point of view on the subject now that she's in her 30s.
"I think sex is great," she said. "But I feel a little different about it now that I'm older. Sometimes I feel like I'm 20 and then sometimes I feel like I'm 50."