There are two types, one is universal and the other is non-universal! Examples are death , war , height , robbery , loneliness etc .; Which is pretty much in everyone! Most of it may be genetic! There are also "Conditioning Fear" (e.g. , frightened by cats and mice that have no real basis!) And "Experienced Fear" (as the name implies!) Which may be included in the non-universal list! Now , the real facts are why do we get scared ? What happened ? This includes new jobs , accidents , new situations , robberies, etc. Another is the fear of one's own siblings! If we analyze the first of these, then the reason will be " Myself" , that is , in all cases the root itself! And the 2nd issues may seem to be not involved themselves, but if you look closely , the " Myself" is coming again indirectly. Why is this thing happening now ? For that we have to go back! When the Reptilians had one thing always working in their brains it was " Fight or flight" which means survival! Through many years of evolution, various branches of that basic thing have sprouted in man! But , the main thing to be afraid of, but only one survival! The question may be, how does fear work ? Some special parts of the brain are responsible for this! Such as thalamus , hypo-thalamus , sensory cortex , hippocampus and amygdala! When I see something scary, it goes to the thalamus, then it has two ways to go, one is "high-road" and the other is "low-road". He has not chosen a path from here! When the "low-road" is not chosen, it comes to the hippocampus through the amygdala, then some physiological changes take place and we are scared! And when it goes to the highroad, it goes through some analysis to see if it's really a scary event! When you do not see it becomes normal again! To give a real example of this, I will talk about a game of childhood when someone was shocked by halum!