ok here we go:
so i sort of agree with what has already been said, that the fire (or whatever it is, i don't think we really know for sure) is ambition. It's what separates him from the masses; everybody else is just a piece of the machine (this is characterized by their dull color). But whatever is inside of him isn't just limited to Ambition, it could be representing something as broad as Life. Naturally, he wants to find a way out of his endless labor, and he does so using the Bliss Product, demonstrating the human inclination to strive for something more, improving himself and climbing the societal ladder. But his fortune lands him right back in the machine, albeit a more important piece. He no longer feels the need to separate himself from others now that he has success, but realizes that he has lost his own "humanity."