Pain is so called bad because it will happen before say you cut yourself accidently at a workshop. You feel the pain then blood comes out and let's say you are about to die. The feeling you feel then you know now to avoid.
It's basically trial-and-error. Sort of.
The main thing with religion and atheists, is that people just don't know. No-body has proof god exists and no-body has proof he doesn't. How can god expect us to believe in him when he gives us no proof he ever was. So then he must not exists, then how does everything come together? So then he must exist.
It's ok to guess about these things because that's what preachers do, they follow a Goddamn book that's been re-written thousands of times and transferred through language.
The worst thing you can do is believe in god to save yourself from hell. It's selfish and you will still go to hell, if hell is or was real.
So since it's not where are we now... back to where we were, no-fucking-where.