There's something going on between what is experienced physically and what is experienced non-physically. They connect, reciprocally, and I think they stabilize each other. There's a coherent metaphysics in operation.
It feels like the danger (well, a danger) for the inquisitive spirit (if you will) is the moment when one side of the system seems to spin on its own without the other. I think that might be what's going on with existential terror? At least in the way I experience it. That kind of terror is a sane response to seeing one side of the system as self-sufficient. I think we can describe this as the experience of sealing oneself off (however briefly) from the unknown. Like getting stuck in the airlock, and feeling the air getting stale.
The system is stable. Massively, gloriously stable. The insight I find serves to enable my conscious navigation and creation. Understanding is a tool of experience, not the ground of experience.
The airlock opens. I emerge, testing, trusting, easing. I have been here before.