Sandra Bullock was hesitant to star in drama "The Blind Side" (out Friday).

"I kept turning it down. Not because I didn't like it, but because I didn't know how to do it," Bullock, 45, told "Extra" at the flick's New York City premiere.

Continued Bullock, "I didn't know how to make it the story that it deserves to be. I couldn't bring to the role what it needed."

See more of "Extra's" raw footage with celebs

Bullock plays a wealthy woman who takes in a homeless teenager with professional football aspirations in the movie, based on a book of the same name.

"I'm glad I did it," she says of the challenging role. "It's still a scary thought for me. I don't know how I did it, but I had a lot of time to prepare for it."

When "Extra's" A.J. Calloway points out that it's the kind of role that could win an award, Bullock responded, "These are the kinds of roles that actresses can mess up, and that's one of the reasons I didn't want to step into it! I didn't know how to make it as good as the story.

"Actresses want to do comedy, and I'm lucky that I get to do it," she said. "I'm just lucky. I get to work."

Tune in to "Extra" Wednesday for more with Bullock -- including how she's spending Thanksgiving!