Here are some factors that contribute to one’s fear:

1.  When we feel separated, fear increases.  A fact is that one does not fear
those he is familiar with (people and surroundings).  Fear arises when there is a
certain feeling of estrangement, which exhibits overall sense or impression of
suspicion.

2.  Attachment to individuals as well as material things associated with one’s
security cause one to fear that one might loose them, so one will do everything
in order to protect one’s relationships, possessions or his self-image.   

3.  Strange surroundings and unfamiliar people bring about fear. Unfamiliar
situations threat one’s security and usually one reacts with extreme caution and
at times, defensive behavior.

4.  One’s negative memory of past experiences where one had either suffered or
witnessed loss, harm or death aggravates fear. The subconscious retains
memories of the past and at certain circumstances, these are ignited.  

5. Imagination at times can create or invent images of trouble, suffering or pain
outside physical truth or reality.  Note that Imagination is never negative,
however when misused and abused, it can bring so much fear in oneself.