Chances are the world will keep on spinning without your product. Happiness should be your primary goal.
Also, though I'm sure you are well-meaning, advising strangers how they ought to live their life makes you sound like a prick.
I'm not saying working on their project doesn't bring them some happiness, but they hardly sound like they're as happy as they could be.
And I'm probably just a prick.
I read the article as a lament. Although maybe I misread and we're both pricks. :D
Sorry, my irony meter just exploded.