The (Nashville) Tennessean said Friday that Underwood, 26, admitted to a history of being emotionally distant to most people, but said she is learning how to be funny and open in front of others.
"I'm getting better with that, but when you open that book and let people in, there's something scary about that. I guess I'm used to keeping people at a distance," the former "American Idol" winner told the Tennessean.
Underwood, who marked 10 No. 1 hits from her first two albums, said since she can be critical of herself, she tends to avoid those publications that remark negatively on her.
"I'm my own worst critic, and I don't need any more negativity in my life. So I go to my Web site and see good reviews and things that make me feel good," she said, referring to her fan club site.
The Tennessean said Underwood, who won the fourth season of "Idol," will serve as co-host of the Country Music Association Awards on Wednesday.