Fear is always of the unknown, there is no other trigger for fear than the mystery hidden within the object of fear. And the greatest of mysteries is you yourself; hence you are your greatest fear. You are the most unpredictable thing there is; you can never be sure of your own actions; you can never be absolutely certain of all your behaviors, motives and intensions.
Who knows what might trigger your anger; what might stir your already unsettled mind; what might capture your imagination and send you on a wild chase of desires. Who knows when your love can become hatred, your compassion can become revenge, and your kindness can become cruelty. To know so little of yourself is the root of all your fears.
If you decide to spend some time to understand it, even a devil (if there is such a thing) cannot scare you; Imagine if you spend a day chatting with the devil, to know where it stays, who are its relatives, what is its purpose of visiting you, how did it become a devil, what are its likes and dislikes!, do you think it can scare you the same way again.
You are in fear only because you have never spent time understanding the devil within you. You have been so busy trying to know everything else; you have forgotten a vicious monster alive inside you that has grown a mind of its own. This monster will continue to trouble and torture you till you decide to spend some time with it alone.
There is a story of a man who accidentally fell into a well during the night. Luckily he held on to the branch of a tree extending from the sides; all night he held on to it with his dear life for the fear of falling and dying.
In the morning when he looked down, he realized that he was only few inches off the ground below; he could have let go off the branch any time. This is the story of all your fears. Almost all your fears are simply a way of clinging in the darkness.
The only way to transcend your fears is to spend some time understanding yourself. The more you know yourself, the lesser will be your fears. Fear loves to dwell inside a confused, aimless and ignorant heart; it hates the clarity of the open sky. Enter inside and find that vast space within you where you can live far away from all your fears.