Memento Mirror Parallels by Jack Clayton

In the flash sideways you would have to be blind to not have picked up on all the characters looking into mirrors and looking as though the remember something suddenly. In Memento the greatest part of the movie comes through these lines:

"I have to believe in a world outside my own mind. I have to believe that my actions still have meaning, even if I can't remember them. I have to believe that when my eyes are closed, the world's still there. Do I believe the world's still there? Is it still out there? . . . Yeah. We all need mirrors to remind ourselves who we are. I'm no different."

He is saying that he can't remember what it is that he's done, but even though it's not in his memory it is still important. This is perhaps a philosophy that inspired the writers to take the path which they have with the story, they like mixing the literal with the metaphorical when it comes to references.