"I forgot the style of acting. I forgot how to speak the style of writing, since it's different than what I've done since," Anderson tells TVGuide.com in the video above. "And also playing her at the age that I am as opposed to the age that I was, I had to give myself permission for that."
See what else Anderson says about playing Scully again in the video above.
The X-Files airs Mondays at 8/7c on Fox.