Fear occupies a space in the heart of every living being in this ecosystem. Fear is nothing but a being's own creation. Let us think about ourselves, we are considered the most intelligent living beings as we know every possible way to survive in this ecosystem. Every member of the ecosystem has something to be afraid of, the smaller member is afraid of getting eaten up by a larger one where as the larger one is afraid of not finding a smaller one. We on the other hand don't have to worry about such things; we cultivate our own food, shelter and whatever else is needed for survival.
If we human beings are so much capable that we can easily do things which will help us to survive, then why be afraid of anything? Actually, the thing is we are the creators of our own fears, there are billions of human beings on this planet and there might be a possibility of a billion types of fear. However, fear can be classified mainly as a feeling of losing something or someone. Usually when a person is very much attached to something or someone, the person starts developing a feeling and that is what defines fear. A person is very much afraid of losing his or her belongings like his house, car, might be a wrist watch, these are some common things. When we go deep, if a person loves someone very much he is afraid of losing that person.
This beautiful thing, abstract thing, called attachment is the main cause of fear. Sometimes you realize it very late that you are attached to something or someone and later when you realize it, you start becoming insecure and insecurity is one form of fear which is most common with the youth.
The only thing that will help you to get of this state of fear is giving up all forms of attachment, that does not mean that you will have to become a monk, one can give up all forms of attachment and lead a life as a normal human being. If someone has something in excess, he can give the excess to someone who needs it, that does not make him a monk and still he gives up attachment and fear has no space.