Believe it or not MHz, I don't suppose I have everything figured out; as I have said before, I am no longer religious.
Scott Free as an Atheist, you will never figure out all of it, an Atheists does not have the certainty of a Fundamentalist, of Christian or Muslim variety.
Thus, I am an Atheist, but can I say with 100% certainty that God doesn’t exist? I cannot, there is no way we can know with 100% certainty, whether God exists, whether afterlife exists etc. However, I think the possibility of existence of God is so small as to be negligible.
As to an afterlife, there is no way to answer the question whether afterlife exists, and which version of the several hundred floating around is the correct one. I take the view that when there is no way of determining if something exists, there is no way of determining its nature, shape or character even if it exists, to me, that is as good as saying that it doesn’t exist.
But with Atheism, there are no certainties. A Fundamentalist Christian is 100% convinced that he is right and those who disagree with him are bound straight for Hell. Same with a Muslim Fundamentalist. He ‘knows’ that all the Non Muslims and non devout Muslims are headed straight for Hell. You won’t find such certainties with Atheism.