One Day

20 years of being apart is sure to a be longgg time. 

on the first day that they met...

dexter : "we will see each other again."

emma: "i know we will."

...and they did see each other again, they meet one day each year on the day they first met for the next 20 years...

'tis sounds so sad :(. you ask why? here are some of the lines that proves it :

emma: "whatever happens tomorrow, we have today...i'll always     remember it... (see what i mean? sounds fatalistic.)
dexter: "maybe we could just be friends" (on the day they met)
dexter: "emma and i were just good friends, and anyway she's not my type" (dexter's answer to her mother's inquiry of the status of his relationship with emma)
dexter:"i'm so much better when your around"... 

 the official trailer

the movie was a story about ENDURING love (maybe). but still i think they should have been together from the start. i'm not so sure if their lives apart from each other was covered in the adage that goes "everything-happens-for-a-reason" kind of stuff or it was just the effect of bad decisions.

maybe, just maybe, they did learn something valuable but i am not sure if those learning where able to compensate the tragedy of emptiness cause by a life lived separately from the one that was meant for you since from the very beginning.

personal opinion: yes, they did realized something in the end... they were meant to be, that what they had since from the start was true love and they have wasted years, emotions, resources on other stuff that they should have spent with each other.