The Oscar-nominated actress is currently dating her Pride and Prejudice co-star Rupert Friend, and admits she pushes him to the limit.
She tells the Elle magazine, "I'm awful. I always have freak-outs. I don't know why anyone puts up with me. I'm mostly an emotional wreck!"
Knightley claims even the smallest problem send her on a downward spiral: "It's stupid s**t. I don't freak out about anything that actually warrants a freak-out.
"That I can deal with. It's the little stuff I can't deal with.
"Anyone who has gone out with me will tell you I have this awful tendency to cry when I get really angry. And I can't stop.
"If I could stop it I would, because I can occasionally come up with some fantastically cutting one-liners in fights.
"I'll come out with one and say, 'Oh, that was great.' But suddenly I'll find I'm crying. And I'll be like, 'S**t, I completely ruined my one-liner.' It's annoying!"
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