You literally believe the same thing either way. Either something always existed or something came from nothing. You believe a highly complex system that is capable of self replication and capable of creating complex systems such as life itself popped into existence. Just the simple interaction such as "this early particle interacted with this early particle to create a reaction" is belief that something existed (a fundamental structure at the very least). Our system is complex and no matter how you try to explain it you either believe: Something came from nothing, or something always existed.