"The Greatest Fear"

Fear is scientifically defined as a chemical based response to a threat. When you think of fear, the classics appear; monsters, spiders, the dark, heights. Then there are fears that you can feel, but can never really detect. They go beyond the physical; they exist only in your mind's eye. Our dreams and life's reality are in a constant state of change. This inner conflict is invisible; a slow paced chess game. But you know, part of the problem that comes with over thinking is that you tend to go over every possible scenario, regardless of it's logic. My greatest fear? That I won't even begin to uncover the question of why I'm here. That I could quite possibly be nothing but an anomaly of nature with no real purpose. Little questions like these that continue to gnaw on my soul far after I stopped sleeping with a nightlight. How can a question be a fear? It's not the question itself, it's the process of attempting to answer them with the limited time and resources we have. Then again, only a person with manic neurons in his head like myself would think so much about this that I would go to this conclusion. Anyway, what do you think your greatest fear is, and are fears like the ones I stated just a result of over thinking, or are they valid?