Religious thinking can be a little dangerous, however, yeah viking mythology, and the different planes of existence is a little historically interesting.
I've pondered the idea of infinity and mobius strip style loop backs on time and space. Deja Vu, and re-incarnations.
Derealization may be putting yourself in touch with a spiritual path.
Not so bad, however, anxiety and spirituality are difficult to wrestle together.
Finding peace with oneself through temperance or free spirit, or mediation or Buddhism may be worth spending some time with. Helped me.
Focus on your health, well being, and everything will be okay.
Autonomous Sensory Meridian Response (works wonders with my anxiety)