I was a materialist for ten years. Now I'm not, but the details aren't germane here.
Atheism does not mean lack of belief, only belief in gods. But that often manifests in an active denial that gods exist, even if still open to some hypothetical evidence in the future. And of course what you believe to be true and false also appears in the way you live your life. In fact, I'm guessing you believe that the natural world will continue to behave the way it has been observed to behave. Strictly speaking, there is no reason to believe this other than the fact that it has mostly worked out so far - but that reasoning requires you to believe that past performance is evidence of future results.
You can't operate without taking something on faith. This faith need not be blind - mine is not - but at some point we have to trust something or someone.