You don’t have to believe in God, but the idea that you would not have fear in the presence of the God who created the universe and is not bounded by its parameters is irrational. If you walk to the edge of a cliff that drops down into a canyon, you have a respectful fear of the danger it creates. Magnify that exponentially. If you witness close up a tornado, even from a safe distance, you know of what I mean.
Add to that the realization that this all-powerful sovereign God is truly holy, meaning there is a universal good. You would immediately be cognizant of the fact that you are anything but. It’s easy to say someone is “good” by a sliding scale human standard. Sure, you have ugly thoughts, may occasionally lie, take advantage of situations when you think you won’t get caught, but others see you as good and you don’t act on your worst thoughts and your little indiscretions didn’t really hurt anyone. Well, place that self rationalization next to a truly holy God and it would be stark, knee shaking, and awe inspiring.
God permits you to dismiss His existence, but if He exists, you will not be in His presence without fear, awe, wonder, etc.