Jessica Chastain was just named the year’s best actress by the National Board of Review for her role in “Zero Dark Thirty,” but she still recalls the preparation it took to get her career going. Explaining there are a lot of actresses in Hollywood but not so many roles, she told us this week at a Peggy Siegal luncheon for her film, “You have to assert yourself in a way where you work when no one is watching. I was always studying, I was always doing play readings even if no one was watching.”