The Theme of the Movie is Simple
The last two words Chuck says in the film are "thank you," and the writer says that is the pivotal theme of the movie. "The idea of acceptance [of his fate], that there is no rationale for some of the things that happen to us. But finally, there is gratitude." The film ends purposely ambiguously, with Chuck at the literal crossroads in Canadian, Texas, deciding whether to follow the woman in the truck or to go down a different path to a new city he's never been to.