Elizabeth McGovern on the pressure of turning "Downton Abbey" into a movie

The highly-anticipated "Downton Abbey" movie is being called "delightful fun." Critics say it invites fans to fall in love with Downton all over again.

The movie is based on the Emmy-winning hit series about the aristocratic Crawley family and their beloved servants. Set in 1927, it centers around the family and staff preparing for a royal visit from the King and Queen of England. 

Oscar-nominated actress Elizabeth McGovern returns as Cora Crawley, the Countess of Grantham. Cora is an American heiress who married the Earl of Grantham, Robert Crawley.

"It was strangely and almost scarily as though we'd never stopped," McGovern told "CBS This Morning." "That thing that happens when you get to a certain age and time just flies so fast. It had been three years since we last shot the series, but as soon as we were all in the house again, it just seemed as though really we were back in the family."

Despite that, McGovern said she felt pressure while filming the movie because of the expectations the show had created for the film.

"I was really relieved that I wasn't the one who had to write it," McGovern said. "Because I did feel a lot of pressure. I mean, I was actually thinking, is this such a good idea? Because people have so much affection for those characters and for that series. And it's a risk."

McGovern said she thought there were several iterations of the script that were thrown out.

"They experimented with different tacks and finally decided, no, we want to give the fans what they want," McGovern said. "We want to go back in time. Indulge in the nostalgia of people missing the series, as much as they miss that era. And just let's hang out with these people that we've spent so much time with and we've invested a lot in, and let's have an adventure."

McGovern said she felt people connected with the show so well because they're nostalgic for a simpler time.

"I think that things are moving so fast at the moment that psychologically we cannot actually keep up with it," McGovern said. "We cannot actually deal with the enormous amount of choice we have, our enormous ability to talk to everyone at any time of the day, the kind of stimulation that is constantly being fed into our brains. And to go back to a place in time where there was no choice. People had a job, they accepted the job for life. People had a role, they were told, and they knew how to behave. If they didn't know, Carson would tell them."

For McGovern, "Downton Abbey" also speaks to the value of good manners.

"I think that's something that this show has reminded people," McGovern said. "To treat each other with respect no matter what our walk of life. The downstairs people are just as interesting to us, to the camera, as the upstairs people. It isn't everything to be the rich guy. And people disagree, but they respect each other as people."

Listen to the "CBS This Morning" podcast with the film's director, Michael Engler: