10/27/2011 09:19 am ET | Updated Dec 27, 2011

Justin Timberlake Gets Uncomfortable With Letterman (VIDEO)

Even the biggest cross-over star in the world can get self-conscious sometimes.

Appearing on "The Late Show" on Wednesday night, Justin Timberlake seemed a little worn out from an exhausting press tour to promote his new film, "In Time." In fact, he had just flown cross country late night after the film's red carpet premiere and screening in Los Angeles. Nice life, if you can get it. But it's not all fun and glamour; as he told host David Letterman, watching yourself in a theater with thousands of people is far from easy.

"It is wildly uncomfortable. For this screening, I wouldn't have stayed but I had basically 40 friends who came to the movie," he told his late night counterpart. After all, they were there to support him -- for once. "I felt like it was the first time they genuinely wanted to see me in a movie, and not Mila Kunis and Cameron Diaz... I sweated a lot... Not good stuff."

Timberlake revealed that his self-criticism goes beyond just seeing a film with lots of other people; he's a perfectionist, even while taking in his work alone.

"You're definitely critical of your performance, always," he said. "But I find the same with music, too. If a song of mine comes on the radio, which sometimes it still does, I find that I naturally want to change the channel. You pick it apart."

That being said, he probably doesn't have to worry about what the rest of the public thinks about his work. He did, after all, bring sexy back.