One does not fear the unknown, but rather, the known.
I came to this conclusion a few years ago and find that situation after situation proves this concept. It is common to hear people say that they are afraid of the unknown, but in reality, the brain can't quite comprehend the unknown. Everything we see, hear, and learn combines to create any fears we may have. We can't come up with something entirely abstract to be fearful of because what we naturally fear what already exists -- that's why we're frightful of it.
For example, many people have a fear of the ocean; they say they are afraid of the deep unknown. I disagree. They are scared of what Finding Nemo has said was down there. They are scared of what Jaws has said was down there. They are scared of what National Geographic has said was down there. They have these fragmented ideas of terrifying possibilities.
Another example is that people fear their future because it is uncertain and undetermined. They profess that they're afraid because they don't know what will happen. What are they really afraid of, though? Likely it is becoming homeless, failing a test, learning of a terminal illness, losing their job, getting a divorce, or any number of known outcomes they've seen in other people's lives. They are afraid of having to sub come to the realities of the people around them.
We aren't afraid of the Boogie Man, we're afraid of what the Boogie Man will do when he crawls out from under our bed. We aren't afraid of death, we're afraid of the idea of ceasing to exist or living in Hell for eternity. We aren't afraid of knives, we're afraid of the pain a knife can inflict. We aren't afraid of relationships, we're afraid of being heartbroken.
The fear that paralyzes so many people is due to what they know, not what they don't.
But why does knowing this matter? Why does knowing that what you're truly afraid of are known outcomes as opposed to the unknown? It matters because your relationship with yourself matters. Knowing what you actually fear instead of making generalizations can only lead to understanding and problem solving.
When you take action in your life to grasp the specifics of your personal fears, you are better able to overcome and face them. Stop making blanket statements of fearing the unknown and begin to notice what you truly fear.