This is why Kristen Stewart never smiles in photos!

Los Angeles - Kristen Stewart insists she isn't miserable.

The 24-year-old actress, who is rarely photographed without her trademark pout, believes she will be branded "a sellout" if she smiles and says she can't please everyone.

The Camp X-Ray star, who split from Robert Pattinson last summer, told the September issue of Elle magazine: "I feel like if I smiled for a paparazzi photo - not that I ever would - that's exactly what people would be desecrating me for. They'd be like, 'Now you're going to give it up, now you're a sellout.' Like, OK, what do you want? What would you like?"

The brunette beauty first realised she was famous when she was snapped smoking a pipe on her front porch with her ex-boyfriend, Michael Angarano, and dog in Los Angeles on the same day the debut Twilight movie hit cinemas in 2008 and despite learning to be more careful about her public image, Kristen takes a more spontaneous approach to her career.

She said: "Never at any point have I sat down and plotted how I should proceed from here on. As soon as you start thinking about your career as a trajectory--like, as if you're going to miss out on some wave or momentum - then you're never doing anything for yourself anyway."

She added: "Then you're truly, actually, specifically working for the public. You're turning yourself into a bag of chips."