Erin, the way you frame your question is somewhat ambiguous. If you are asking how an atheist can bear the thought of there not being a God, that’s one question. If you are asking how an atheist can conclude that there is no God, that’s another. Those are questions that each person would have to answer for himself, if he can. You are presuming that something you have (faith) is so essential to everyone that those who do not have it feel its absence. That’s a little like a bird asking a squirrel how it can bear not to fly. On the other hand if you are asking how anyone, atheist or not, can believe in evolution that’s yet a different question which I’ll try to answer. Evolution, whether of the human being or of the universe as a whole, is not incompatible with the belief in God; it is only incompatible with your beliefs, presumably your literal interpretation of the Bible. There are other interpretations of the Bible, and other beliefs which don’t include the Bible. There are plenty of people who believe in both a Divine Creator and evolution, and to presume that those two are incompatible is to deny God the privilege and power of creating the universe any way He chose.