Mandy Moore teases what's next for Rebecca in final 'This Is Us' season: 'It's really gutting'

The This Is Us cast were all smiles at the season 6 premiere event at Paramount Pictures Studios in Los Angeles on Tuesday night (Dec. 15), but fans of the smash NBC drama need to prepare for plenty of crying once the sixth and final season actually premieres Jan. 4.

With People, the acclaimed and beloved ensemble cast previewed what can be expected for each character. Mandy Moore painted an especially heartbreaking picture for Pearson matriarch Rebecca, who has been suffering from Alzheimer's:

"It's really gutting. It's really sad, just so heartbreaking. It's weird because I'm sort of on this parallel journey of saying goodbye to my family here and what this experience has been. Rebecca is also sort of slowly reflecting back on her life, starting to say goodbye and making her wishes known—really just savoring the time that she has left and being as present as possible.

"It's really challenging. It's challenging not to let my grief of her situation influence what she's going through because she is handling this situation with so much grace and honesty. She's very intentional about what she wants from her life right now and how she wants to live it. The plan she makes, it's really something, but it's hard."

The official trailer for the farewell season, released on Thanksgiving Day, teased through the eyes of Rebecca as she grapples with losing her memory: