I can definitely relate to one of the things you named. Aging terrifies me. I really don't see how people that get to live to 80 and older are seen as lucky, considering how human body and mind slowly and inevitably deteriorates over time.
So for me it would be:
- Aging, deterioration and horrible illnesses that often come with old age, and inevitability of it
- War
- Being locked inside a scary/painful psychotic state. That's what happened to my grandmother in the last days of her life and seeing how she passed horrifies me in a way I cannot even describe.
These are the deep dark fears that are always lurking in the back of my mind.