I heard a really great description of this the other day

Imagine you’re an ant. Your world is small and scent based, your life is simple and straightforward

Now imagine you experienced a human perspective. You feel the stress and anxiety of something as abstract as money, you know of events on the other side of the world - you understand that there is a world, and how walking in one direction long enough would bring you back here. You see the beauty of the sunset, and dream of traveling to space

You see how humans see ants

You also understand where food is stored, what ant traps are, and the layout of the surrounding area your colony has yet to explore - things incredibly useful for an ant

Now you’re an ant again. Your ant brain can’t hold onto this knowledge, but you have a notion of what you saw.

You know you found all the food everywhere, and learned of hidden dangers to your colony… But you can’t remember the knowledge. You saw impossible ways to travel, but they no longer make any sense. You know the humans see you as pests, just minor annoyances in lives filled with emotions you don’t understand. You know they were scared of something… But what could threaten such a being? Another ant touches you to see if you’re alright, and you want to scream and vomit using organs you don’t have

That’s cosmic horror