I don´t get it.....

(Spoilers)
Apparently, most of what was going on in the movie is just his imagination. I only know this from reading posts here. It´s not that I have a problem with movies with dream-sequences or the like (I think Boxing Helena is great), but in this movie, I had no clue. Not even after having it explained can I figure out what was imagination and what was not.

Despite the great acting and great build-up, the ending is just too flat.