Fear adds vulnerability to our existence. The smartest in the world were initially scared to venture out. Many people die and go to the grave without fulfilling or taking a bet they were bullish on for decades.
Fear comes from upbringing and availability as well. If from the start, you are told what you cannot do, and not appreciated for your small wins, no matter what: you will avoid venturing out.
The only reality of life is that we are dying every second. But what is the point of living life with fear? You must believe in yourself more, go against the odds to win over your fear, and die peacefully because you tried.