Fear is not a sense of security or safety; it is the anticipation of failure or disaster. Everyone faces fears on a daily basis, whether it is something simple, like the fear of being late for an appointment or class, or something larger, such as the fear of heights. Most fears are learned, but some are instinctive.
The survival of the human race relies on instinctive fears such as being afraid of heights or of spiders. If we were not afraid of heights, we may try to do something idiotic like jump off a two-story building or play with a black widow spider. If we did not have these natural fears, we would have to learn, either by first-hand experience or by being taught these fears. The first option is not very good since many people would probably become seriously injured or die as a result. To be taught a fear, however, does not always work.
Most everyone has had their mother tell them not to touch the stove because it is hot. But what do we end up doing?--we touch it. Without instinctive fears, there would be much higher accident and death rates because people would not know there is something to be afraid until they experience it.
Some fears we often confuse as common sense, such as the fear of touching a hot stove or the fear of being cold if one does not wear enough clothing when it is cold. Since almost everyone has had experiences like these, we consider it common knowledge instead of an actual fear. Our personal experiences we have through life, tells us what we should or should not be afraid of. Other people can also affect our fears through the sharing of their own personal experiences.