"I have to say really, I feel better than I ever felt in my life," Aniston says on The Ellen DeGeneres Show, airing Friday. "I did have a moment, though, over the weekend my first like huh. … I don't want to [turn 40]."
The cause of her hesitation?
"I found a really long gray hair and it kind of flipped me out," she tells the talk show host. "It's not my first but it's the fact that it was so long. I was like, 'Oh that's been there. How many others are there, and what does that mean? It actually brought me to tears slightly."
DeGeneres pressed Aniston to reveal some guests for her birthday celebration on Saturday. "Courteney Cox … she's going to be invited to the party," DeGeneres said, holding up a photo of Aniston's longtime friend.
"She's invited to my party on Saturday," Aniston confirmed.
"He'll go," DeGeneres continued while holding up a photo David Arquette. "And he'll probably go right?" she added showing a picture of Aniston's boyfriend, John Mayer, wearing a one-piece green bathing suit.
Avoiding the question, Aniston joked, "I've got to tell you honestly I almost don't want to touch it." She then added, "The man's got balls. What can I say? I think he's funny."