Sienna Miller says the biggest lesson she's learned this year is "hold your cards close to your vest."

"I've got a huge mouth, especially when it comes to my business," the 24-year-old actress tells Life magazine in its Dec. 30 issue. "But I've realized that if you start talking about things, you open up a floodgate."

Miller's engagement to her "Alfie" co-star Jude Law appeared to fall apart after Law publicly apologized in July for having an affair with his children's nanny. Reports in recent weeks had suggested the couple were back together.

"I find it odd that people ask me things like, 'Why did you take [Jude Law] back?' I don't regret anything," she tells the magazine.

Miller stars in "Casanova," which opened in U.S. theaters on Christmas Day.

When asked who is a modern-day Casanova, she replied: "I don't know. ... People think I should be an expert on love, and I haven't got a clue."

Miller and Law became engaged last December. Law divorced fashion designer-actress Sadie Frost in October 2003 after a six-year marriage and three children.