The Titanic actress is happier than ever right now, with a marriage to Sir Richard Branson's nephew Ned Rocknoll, three young children and a phenomenally successful movie career.
Speaking to ITV's Lorraine, she said: "I'm 40 this year. I'm very excited about it actually I have to say. I think the last couple of years I've done a lot, had the baby, creatively it's been just really interesting, diverse and sort of fulfilling time for me.
"I kind of feel like when I get to that 40th birthday I will have earned it you know. And I have this strange notion that I'm going to spend the day in a bikini, I don't know why I sort of decided that but I just want to feel great and vital, and all the things I do actually feel and so I'm looking forward to it, yeah I am looking forward to it."
Kate, who turns 40 on 5 October, gave birth to third child Bear Winslet in December 2013. She's also mum to son Joe, from her marriage to director Sam Mendes, and daughter Mia from her marriage to first husband Jim Threapleton.
She said of her children: "They really do respect and enjoy being on a film set and they are fascinated by it. They don't kind of run around like kids who know the ropes or anything like that, they are really not sort of on-set type of kids in that way.
"That's enjoyable for me because I do feel as though perhaps I'm just passing a little of the work ethic along to them which is really, really nice to see and to be able to do so hopefully Baby Bear will get some of the same thing."
Kate can next be seen in Insurgent, the sequel to last year's Divergent, based on the franchise of novels by Veronica Roth.
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