"He doesn't like to be reminded about getting older," a friend explained. "He didn't even want a birthday cake. He says, 'It's my job to look good.'"

And an insider told the magazine, "The obsession with his looks has gotten worse very recently. It's hit him pretty hard that he's not looking as young as he was."

Apparently, Brad's early reputation as a Tinseltown hottie makes those fine lines harder to handle.

"When he first hit Hollywood, Brad's natural good looks helped him immensely, but as he has gotten older, he is finding it more and more difficult to maintain them."

So how does the two-time winner of People magazine’s Sexiest Man Alive turn back the clock? Pitt's not going for the traditional Hollywood health food and yoga approach. Instead he's hitting the town with pals, enjoying a few drinks and sneaking "cigs behind (Angelina Jolie's) back," another Star source revealed.

While she doesn't approve of the smokes, Jolie is willing to indulge one of Brad's other youthful, bad-boy props. Angie presented him with a US$100,000 custom-built motorcycle for his birthday.

"He makes sure to ride every day," the insider dished. "It makes him feel young. It's the rebel in Brad. It's hard for him to let go."