Casey Affleck and Michelle Williams on the Emotionally 'Painful' Experience of Making 'Manchester by the Sea'

Kenneth Lonergan’s new drama, Manchester by the Sea, is an emotionally devastating and powerful film about family, loss, and forgiveness. It’s the type of film that can haunt you for months afterwards — and that’s after only two hours of watching.

Imagine then how the subject matter affected the cast, which spent weeks filming Manchester. “It was painful,” Casey Affleck told Yahoo Movies (watch above). Affleck plays Lee Chandler, a Boston plumber called to the titular coastal town to watch after his nephew (breakout star Lucas Hedges) after the death of his brother (Kyle Chandler). “The hard days when you’re an actor mean showing up and really trying to get yourself to feel terrible… and be genuinely crying.”

Related: Kenneth Lonergan Goes Deep on ‘Manchester by the Sea’ and Getting Over ‘Margaret’

Michelle Williams, who plays Lee’s ex-wife, Randi, said Manchester is the type of film she’s wanted to do since she was in her late teens. “When you get this part you’re so excited and at the same time you’re sort of dreading it because it’s not a comfortable place to go,” she told us. “So it’s like an equal mix of excitement and gratitude and dread and anxiety.”

Affleck, however, explained how such a trip through the emotional wringer can ultimately lead to a positive outcome. “At the end of this movie I really felt like I’d learned a lot. I was a better an actor, I felt full and satisfied and grateful for the experience and opportunity to grow.”

Manchester by the Sea is now playing in select theaters. Watch Affleck explain how the film was almost directed by Matt Damon and starred John Krasinski: