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Cameron Diaz wore an itsy bitsy green bikini while vacationing in Hawaii Tuesday. (See more Diaz bikini pics!)

Despite her rockin' bod, the My Sister's Keeper star -- who turned 37 last month -- recently told Parade she doesn't always feel sexy.

Can you guess whose bikini bod this is?

Asked if she has "ugly" days, she said, "Oh, sh yeah. I have them. I don't declare myself as one of the most beautiful women in Hollywood. That's other people's label. I don't think that self-deprecation is healthy for people. I think you should have a healthy relationship with yourself. And so we all have our 'up' days and we all have our 'down' days. But I'm not going to walk through this world hating myself because somebody else doesn't think I'm pretty. All I can do is know how I feel about myself."

Check out what Cameron Diaz used to look like

She also she is not afraid to grow old.

See what Cameron Diaz looks lie without makeup on

"I have no problem with it. It's wonderful," she told Parade. "Thank God we get older because if we're not getting older, we're dead. This is a much better option, to be getting older. And if we're not going forward, then we're stagnant, and we're stuck. And I've been stuck before. And I don't like it. It's not fun."