I grew up Jewish. I have lost my faith, but that quote is still fundamental to how I see my place in the world.

I'm an atheist but I really like:

>Therefore man was created single in the world to teach that for anybody who destroys a single life it is counted as if he destroyed an entire world, and for anybody who preserves a single life it is counted as if he preserved an entire world.

(Directly from the Mishna in the Talmud Yerushalmi)