It all depends. If it were, say, the hand of God coming down and killing all the nonbelievers, I'd probably be saying, "No fucking way!" until he got to me.

If it was the more predictable nuclear destruction, I'd just find a good spot to see a nice big shroom cloud up close before being turned into a fine dust.

Comet? I'd try to survive. Who knows, maybe it'd work.

OR, if it was ACTUALLY happening, I'd react just like everyone else. I'd shit my pants and cry 'till I died.