The British actress had been without an Oscar win since her first nominations for Sense and Sensibility in 1996 and Titanic in 1998, until taking home the statuette for Best Actress earlier this year (Feb09).
And the 33 year old admits she feels she's now forced to live up to an impossible standard, and can't be true to her free spirit.
She tells America's Harper's Bazaar magazine, "It's very hard to feel like yourself because you're not; you're on show. In the old days I'd just wing it, but now you need to give people what they want, which is someone looking composed, fresh and put together. Our knickers will still go up our a** at the most inappropriate moment. And we'll still want to flick them out, but you can't, because someone is going to catch you.'".