My sense was that the main idea is that people in industrialized society have become estranged from their mystical connection to nature, from their mystical selves. In those final scenes, he reaches his true self, recognizes his former being as just a mask. Momentarily, he tries to hold onto his now unmasked self, but having entered the dreamworld (and having perceived that an apocalypse is imminent), he sheds his earthly, limited self and emerges ready to die and thereby achieve spiritual truth.
Yeah, that kind of makes sense, although I'm guessing you meant to say that he tries to hold onto to his former masked self, rather than his now unmasked self. For me this is the most mysterious scene of the film, yet perhaps also the key scene.