It is possible, nigh probable, that what we experience as the “fear of the Unknown” is really a case of mistaken identity. Some stalwart souls attempt to see such a fear from the ‘glass is half full’ perspective, reframing it to be the Great Mystery, the Unknown or Emptiness to be discovered and explored.
Such a lofty approach is certainly one way to deal with the fear or anxiety, but it doesn’t really get to the heart of what causes the misperception in the first place: the Mistaken Identity. 
Countless books and teachings are devoted to helping humanity cope with this underlying anxiety, from the head-on approach of debunking fears (through cognitive behavioral therapy) to practicing affirmations (e.g., your negative thoughts are an illusion, don’t believe them, believe these thoughts instead).
Each approach touches on, but doesn’t quite penetrate to the core of what birthed the fear, what births all ‘fears’ of the Unknown, nor what nourishes and feeds each new crop. The Mind. It is as simple and as complex as that – the mistaken identity is defining the Unknown as the source of fear, rather it is our beliefs about the Unknown that amp us up and put us on alert.