Here's my opinion:
Religion, to me, exists to fill up a lot of gaps in humankind, like the questions of where we come from, what happens when we die, what we live for, etc. However, I also think logically, and religion just doesn't make any logical sense. I have yet to find one real reason to believe in a deity of any kind.
So, I answer the questions in my own way. Where did we come from? I don't know. That doesn't mean that there has to be a god, though.
What happens when we die? We cease to exist. In the same way Christians believe animals (who have no souls) just die, so too do we. It's sad, but, in my opinion, realistic.
What do we live for? I don't think there is a purpose to life. I think it just is, and we have to make the most out of it before it's gone. I want to experience life the best I can, because it's the only one I get.