I am totally a fatalist. It is not fun. The smallest twinge, tic, or tickle immediately is translated into any number of serious and mostly fatal ailments. If a family member is 10 minutes late and I can't reach them by phone my mind whips up a dire scenario. They've been kidnapped or had an accident.
Certainly I have worked to change the story my mind weaves and have made progress over the years, but still the fatalism can creep into an ordinary situation and there I am stuck in the worst case scenario once again.
My mother and her mother before her were both pessimists so there are genetics involved.
I think I always tended to think in this manner, but it became habitual after the death of my husband when I was 21 and then was further cemented by my granddaughter's passing at age 2. Both died in accidents.
No therapy nor head meds have fixed me. Meditation helps tremendously. Distraction is another great tool.
I seriously envy the optimists in this world.