If you believe you can create something, then you believe you have free will. And If you believe you have free will, then you believe in final causality or
teleology (which presupposes God). Unfortunately, as an atheist, you're not allowed to invoke God to rationally justify a belief in final causality and free will. And since you can't rationally justify a belief in free will, then you must accept that you cannot create anything. You do not create your own purpose because your disbelief precludes the very possibility. To reiterate: Atheism is an absurd worldview because it views the world as ultimately purposeless and meaningless and therefore absurd.