Fear is originally born as a result of repeated heavy and traumatic 'emotional' experiences in early life. These experiences occurred when we were kids and unable to process what was going on, and therefore developed coping strategies at a sub-conscious level. This 'coping' is a mixture of 'fantasy' and 'reality'. 'Fear' is deep, it is complex and this is partly why 'fear' is so hard to pin-point accurately.
Because the intense early experiences remain unprocessed and unacknowledged, they have an effect throughout life, whereby 'reactions' to situations are governed more by the subconscious processes than the 'rational' mind. Do we know why we get angry, or sad? Why we have anxiety? Is it 'just the way it is' and we have to accept it?
Fear is triggered 'at the subconscious level'. Although the 'conscious' mind tries to label and identify the 'cause' of fear, this usually turns out to be the 'trigger', and not the 'cause' of fear. The trigger (eg threat of loss of job/spouse etc) exposes the complex psychological state of fear manifestation (anxiety, worry, terror etc).
Unless one goes back and explores the 'original' settings in which these fears developed, it will be very difficult to be free of them. But this IS possible, it can be done, and it is a BRAVE undertaking to really and truly 'face one's fears'! However, one needs to take responsibility for one's feelings - blaming the the 'current' event or person that triggers the fear is simply to play the old game and to remain in perpetual confusion and misery. Eventuallly, FEAR is revealed for the imposter it is: "False Evidence Appearing Real".