People have all kinds of fears.
Fear of the dark, height, spiders, small spaces, large spaces. All kind of phobias exist. But I would say Phobophobia is the weirdest and one of the scariest.
It's the fear of fear itself or of having a phobia. It's a phobia that goes around in circles. Knowing you fear these kinds of things and additionally you know you have this fear could be... frightening.
Fears are interesting, thinking about them is interesting but only if you don't have phobias. Sometimes it's hard to even know if you have a phobia of some sort, as there can be one for everything and anything.