There are a very few things that are literally borne into the nature of human behavior (psychology). Fear is one of those very few things. It is an absolute base instinct. No child is born without it. Fear is a necessary evil for survival. If we let it take over our beings completely, fear can ruin our lives. If we don't exhibit enough of it to stay out of danger, lack of fear can kill us. What causes fear? Is there anything we can do to minimize it? If we minimize it, is that healthy? Legitimate questions, all. Let's start with basic causality.
Why is fear absolutely innate? As infant children, we are exposed to new things by the minute. As a survival tool, we have a tendency to fear the unknown. To the mind of a child, everything is an unknown. The moment a child is born, (s)he is exposed to cold for the first time. That's enough to make the child cry. This is a new and unpleasant sensation. As infants are prone to do, we typically adjust and adapt to this very quickly. We may not love the cold, but as a whole, we've learned not to fear it, by day one. Still, new things are exposed to us every day. In the most natural sense, fear is instinctual.
A little bit of fear is actually a healthy thing. I own a dog. I love dogs. Still, if I approach a dog and it begins to growl at me, I'm not going out of my way to pet it. Fair or not, if this dog has taken an instant dislike to me, I'm not going to tempt fate. I have a natural fear and aversion to deeply embedded teeth marks in my skin. Fear is a survivor's tool. However, if we let fear control us, rather than controlling it, fear is a detriment. In the above example, I'm not going to let the fear of a growling dog make me so afraid of dogs, in general, as to refuse to own, or even pet, one. Fear is necessary for survival, but it needs to be kept in check. There are people who live with so much fear, they refuse to leave the house. This is not healthy.
So, how do we minimize fear? First, we have to recognize why something creates fear in us. Fear of the unknown is one thing and is natural. But, we can't let fear prevent us from attempting to know the unknown. On the other hand, fear of something we already know can cause us to freeze and refuse anything. Generally, this kind of fear is based on some kind of trauma. If you've seen or heard or felt something negative and you associate it with a particular object (or place or person), you may end up with an unnatural aversion to that person, place or thing. Fear to this depth is often called a phobia and is not healthy. The best way to minimize fears is to face them. This is often easier said than done, but it is a necessity if one is to live a fairly normal life. A quick personal example. Just about a year ago, I was in a car wreck at an intersection right in front of my work place. Now, the first few (several, actually) times after that wreck, I was a little fearful approaching that intersection-especially as I entered the left hand turn (which was what I was doing when the wreck happened). But, the fact of the matter is, I have to make that turn to get to work. So, fear or not, I face that turn five days out of seven. I have to face my fear to have a livelihood.
Now, I'm not saying we all need to become daredevils who have no fear. (Frankly, I don't believe these daredevils are truly fearless. Rather, I believe they have the fear, but get off on the adrenalin rush associated with fear.) But, truthfully, I'd rather live as the daredevils do, than do the opposite and never leave the house. Yes, too little fear can kill you. But, too much fear can make you afraid to live. To me, that's the far-worse scenario.