Donna Freydkin, USA TODAY

So the thing is, once you open the door, it's really hard to shut it again. Almost impossible, in fact. Which is why so many celebrities (Natalie Portman and Penelope Cruz, among them) refuse to reveal much about their private lives from the outset.

And then there's those who try to go back. We're talking about Ashton Kutcher, who flaunted his relationship with Demi Moore while the two were together. They professed their love for one another to anyone and everyone, on Twitter, in interviews, on red carpets, you name it.

Now that they've split and he's dating Mila Kunis, he's taking a different approach.

"You know, I've learned the hard way how valuable privacy is," he tells Elle. "And I've learned that there are a lot of things in your life that really benefit from being private. And relationships are one of them. And I am going to do everything in my power to have this relationship be private."

Moore and Kutcher separated in November 2011 and he filed for divorce last December.

Kunis made headlines of her own for her adorable interview with a newbie British reporter while promoting Oz the Great and Powerful.

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