"Motherhood was not an urge I couldn't resist, it was more like a thought I'd been thinking for a very long time," says Keaton, who celebrates her 62nd birthday Saturday. "So I plunged in."
The Oscar-winning actress, whose past romantic partners include Woody Allen and Warren Beatty, adopted daughter Dexter, now 12, and son Duke, 7.
"I've had such an unusual life. Obviously career-oriented. I was happy to be a daughter well into my 40s. That was something that meant a lot to me," Keaton tells Ladies' Home Journal in its February issue, on newsstands next Tuesday. "I didn't think that I was ever going to be prepared to be a mother."
She "had years of selfishness," Keaton says, but being a mother is better.
"You can't sit there and go, poor me."
Like many mothers, Keaton is capable of embarrassing her children.
Keaton co-stars with Queen Latifah and Katie Holmes in the upcoming film "Mad Money," about three Federal Reserve Bank employees who plot to steal money that is about to be destroyed.
Holmes "took that role and played with it, she was running around, constantly dancing," Keaton says. "She's courageous and adventurous and wants - and is having - a very big life. And she's handling it with such grace. I wish I could have done that."
Keaton won an Oscar for "Annie Hall." Her screen credits also include "Manhattan," "Reds," "Looking for Mr. Goodbar" and "Marvin's Room."