The opposite of fear is faith. It's a marriage of the mind, body, and soul. Admittedly so, I struggle with this on a regular basis. My intellect knows that my thoughts are what limit me. Sure, environment and upbringing have programmed us to a point, but I am the one who most of all limits myself.
Cliché:
Fear = "False Evidence Appearing Real"
Today, I choose Fearlessness.