I too remember feeling like I was dying. My consciousness had dissolved and transformed to such an extent that "will I ever be a human living on Earth again? What's stopping me from just being here forever? What's stopping this five minutes as five million years?" Basically every assumption about reality is broken, "real life" takes on a new sense of impermanence. Being alive here at all starts to feel like a fluke, like a hundred-year stop in a trillion-year journey.

I might be full of shit though.