As a nonreligious person, where do you get your moral guidance?

[Anomalocaris]

I was raised Christian, so "do unto others as you would have them do unto you" is deeply ingrained and I saw no reason to discard that particular bit.

The golden rule's utility is largely because it's older than christianity.

I think the golden rule harkens all the way back to when two similarly sized reptilian predators in the swamps of the carboniferous era sized each other up, and each calculating “if I don’t try to eat him, maybe he won’t try to eat me”.

religion merely made generations dumb enough to think making cantaloup sized brain do what sunflower seed sized brain had been doing for hundreds of millions of years takes divine inspiration that only itself can provide.