As a child this question always made me nauseous. I could not contemplate non-existence or what might be if the universe wasn't. I could also never comprehend eternity or everlasting life, and pondered whether I could ask God not to be immortal.
Now the NYTimes has an article wherein this very question is asked of a variety of thinkers.
Are you astonished by being?
No wonder the philosopher Robert Nozick said that “someone who proposes a nonstrange answer shows he didn’t understand the question.” Nozick’s own hypotheses were certainly strange. One was that the primal nothingness might have been so annihilating that it annihilated itself, thus producing being. This echoes a much-mocked line of Heidegger’s: “nothing noths” (“Das Nichts nichtet”). Silly as it sounds, this captures the sheer uncanniness of the Big Bang — and, as Heidegger said, the anxiety we feel in the thought of “nothing” brings us face to face with Being itself.