Some will still believe in religion, and just hold themselevs up in their basements/churches/shelters/etc while fervently praying and reedeeming. The rest of us will be doing everything we've ever wanted to do, but couldn't. There would be no more such thing as sanity. There would be no more status quo. Just chaos. You might as well grasp it and enjoy a sense of elation you could never get otherwise. You're going to die anyway, and so is everyone else in the world, so go primal and fuck it all.
Enjoy it while it lasts.