In The Parent Trap, British actress Hayley Mills plays identical twins who don’t know the other one exists until they meet at summer camp. Realizing they are each being raised by one half of a divorced couple, the girls switch places in a plot to reunite their family. This sweet comedy, which also starred Maureen O’Hara and Brian Keith, became a hit in 1961 and cemented Hayley’s reputation as America’s favorite child actor.

Yet her life was no Cinderella story. Hayley starred in six films for the Walt Disney Company, including Pollyanna and That Darn Cat!, but suffered from crippling self-doubt in adulthood. She lost her fortune to taxes, married and divorced a much older man and struggled with bulimia.

“Problems never go away however rich or famous you become,” Hayley, 75, who recounts her life story in the new memoir Forever Young, exclusively tells Closer Weekly, on newsstands now. “In fact, they can become even worse if you’re in the public eye.”

Her parents, actor Sir John Mills and playwright Mary Hayley Bell, were already famous by the time Hayley and her future actress sister, Juliet Mills, and brother Jonathan were born. But Hayley never seriously considered acting professionally until she joined her father on the set of 1959’s Tiger Bay. Her performance caught the attention of Disney founder Walt, who signed her to a six-picture contract.

“In the early days, I loved what I was doing,” says Hayley, who called Walt a “surrogate father.” “He genuinely loved children, had a lovely sense of humor and was really easy to talk to because he listened.”

Hayley Mills 'The Parent Trap'

Walt also liked to have fun. Hayley remembers spending two days at Disneyland with a group of other young stars like The Mickey Mouse Club’s Annette Funicello. “[Walt] walked everywhere and went on all the rides with us — even the teacups,” Hayley recalls.

But at 18, Hayley did not renew her contract with the Walt Disney Company. She felt she had been held back by being forced to turn down projects like 1962’s racy Lolita, but she didn’t realize how hard it would be to find jobs as an adult.

“It was quite difficult because I didn’t really know who I was,” says Hayley, who began to feel like an impostor. “I hadn’t gone to drama school. For the longest time, I thought my success was some dreadful cosmic mistake.”

At 25, she married English filmmaker Roy Boulting, who was 32 years her senior. The union drew scorn from some former fans. “Age has never been a criteria for me. I grew up surrounded by adults,” Hayley explains. The marriage only lasted four years, but it produced son Crispian Mills and helped Hayley win her battle with bulimia. “I was going to have a baby, and I had to take care of myself so it just kind of went away,” she says of her eating issues.

Today, Hayley feels sure of herself and grounded. “I’m a mother. I’ve got five grandchildren. I have an amazing partner; we’ve been together 24 years,” says this still working actress. “I’m proud that I’ve survived my life. The advantages of being the age I am now are enormous because I’ve learned so much. I’ve acquired quite a bit of wisdom.”

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For more on this story, pick up the latest issue of Closer magazine, on newsstands now.