Whenever your character has a really strong backstory, one of the questions you need to ask yourself is: Does the movie take place then or does the movie take place now? Is this a movie about the present or a movie about the past? Or is it truly about both?

As  Manchester By The Sea demonstrates, flashbacks work best when the most interesting part of the story takes place in the story between the past and the present. When two powerful stories are in dialogue with each other. And they work least the most interesting part of story is the stuff that’s happening in the past, or when the flashbacks exist to explain things to the audience, rather than to allow the character to wrestle with them himself.

But the most exciting thing about Manchester by the Sea is not just its use of flashbacks, but the unusual structure in which those flashbacks occur. A structure in which rather than changing over the course of the story, the main character refuses to change..."