Answer: Fear is an unfulfilled desire on a certain level that gives a person the feeling of a lack of filling.
Fear can be dulled by medications, drugs, alcohol, and so forth, but for Kabbalists, the feeling of fear is encouraged and supported because it enables a person to work on the fear in order to rise above it.
After all, everything we undergo is according to the Creator’s guidance, which means that I must feel and experience this feeling, but I need not remain in it. One moment is enough. I must work that way in order to eradicate all of the negative feelings that I have by turning them into positive ones, but I cannot ignore them!
From the Kabbalah Lesson in Russian 3/13/16