“That which does not kill me makes me stronger” (or “Quod non me destruit, me nutrit” in Latin)
— Friedrich Nietzsche, Twilight of the Idols, 1888
German philosopher (1844 – 1900)

In becoming fearless, you must remember that setbacks are not bad, they only strengthen you.  These moments of fear, however real and physical, can be leveraged in the same way that martial artists leverage the weight of their opponent against them.  If you look at an event as a negative impact that cannot be overcome you have lost.  The moment you recognize the glass is still have full you have overcome that fear and are reborn as a soldier of positive thought.

Nietzsche was correct in that hard times make us stronger individuals that are better able to navigate the treacherous waters ahead.  No doubt there will be high and low points in your life, but what makes you who you are is how you react to these highs and lows in life.  Be humble during the high points and strong during the low points.