Few characters have grown more during the course of Mad Men's seven seasons than Peggy Olsen.

In the exclusive video above, Elisabeth Moss looks back on Peggy's journey from a nervous 20-year-old secretary to the confident ad woman she's become in the final season's homestretch. "She grows up," Moss says of her character's decade-long evolution. "She becomes harder in a lot of ways. She gets her heart broken; she has bitter moments. ... But I hope that she still retains that sense of honesty and positivity and truth. She's earnest. She very much believes in whatever she's saying. I think she still has that despite the fact that she's had some hard knocks."

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Although Moss believes Peggy's earnestness has sometimes led her astray, the actress doesn't view it as a character flaw. In fact, she says it's what sets her apart from Don (Jon Hamm) and other characters on the show.

"She could have very easily grown up to become like Don, and she's not," Moss says. "She could have gone in that direction easily, but she's going the other way. She is the story of hope. He's the story of this sort of failure of a man and she's the story of this hope for the next generation."

Below, check out two exclusive images of Peggy with Don and Joan (Christina Hendricks), two of her mentors along the way. Mad Men's final seven episodes premiere Sunday, April 5 at 10/9c on AMC.