Fear is one of the biggest problems that face the man.
It's like a student who has exams; he/she is fearful of the exam
It's like a man whose body is sensitive towards the catch cold, so that he/she be fearful while being whether is a cold or hot place, lest he/she would catch a cold
Like a man who fears the future while being reassured, but other people be troubled.
There are some people who are fearful to the extent of having phobia whether of heights or wide places or water, etc