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A non-religious answer, interesting, I think it all comes down to beliefs though, even atheists have to find something to believe in, other wise they would be swallowed by nihilism and get depressed.
Your example is pretty good (what's the name of this manga btw?), although I think a glimpse of joy is only the first step to finding purpose in life.

I didn't want to name the manga because of some of it's "content," but oh well... It's called "Ai-Ren."

(I love the title because it means Lover in Chinese, contains the Kanji for "person" and has the name of the heroine Ai which can also be seen as "AI.")