Kristen Stewart says she is miserable

London: Actress Kristen Stewart admits she is "miserable" and never sure when she is happy.The 22-year-old, who recently split from her Twilight co-star and boyfriend Robert Pattinson after she was caught cheating with director Rupert Sanders, admits that she occasionally finds happiness when she is pushing herself "to the limits", but otherwise tends to be sad.[caption id="attachment_489447" align="alignleft" width="380"] Kristen Stewart and Robert Pattinson[/caption]"I'm a miserable. I'm not sure if I'm most happy when I'm comfortable and content or when I'm pushing myself to the limits. There are such different versions of happy. And I really appreciate both," femaelfirst.co.uk quoted Stewart as saying.IANS