The Onion AV Club interviewed Jennifer Beals, star of Flashdance et al, and she very succinctly stated an important aspect of the problem of celebrity:
“Because as I’m watching the film and people are reacting to the character on the screen, I’m realizing that more people are engaging with her than know me, and she is in some ways more real than I am to those people by virtue of this focus. I knew intuitively that people were going to confuse her for me and me for her, and that that wasn’t true, and that that wasn’t real. So in a moment of existential crisis, I found myself in the bathroom. I locked myself in the bathroom of the theater. Because they had, like, one little room where you could lock yourself in. My brothers had to come get me. [Laughs.] Of course, the surest way to free yourself from an existential crisis is through comedy, so they made me laugh, and I got over it and went and celebrated the film. But it was hard. It’s hard to be in the center of anybody’s gaze, you know? It’s hard to be the center of attention.”
It’s like having a evil twin. The problem’s worst for actors–because the twin has your same face and voice–but it applies to all celebrities to some degree. There’s another of you, wandering about, and what they do defines you.