Fear
Fear is an emotion that is characterised by an intense and unpleasant feeling induced by the perception of real or presumed danger, concerning either the present or the future. Fear is a primary emotion derived from an innate aversion of risk or threat. Fear is something present in both humans and animals alike. From a psychological standpoint, fear is an intuitive, emotional state that is necessary for an organism to adapt appropriately to an environment, more often than not, producing distress.
Fear functions in the following way: the limbic system focuses its attention on that which is a threat and the frontal lobes (in charge of directing conscious attention from one thing to another) are partially deactivated. During a panic attack, a body's conscious attention is fixed on the apparent source of danger. A subsequent increase in heart-rate is interpreted by the subject as a legitimate confirmation of the existing threat, which in turn feeds fear with more fear, consequently impeding an objective interpretation of the real threat. When manifested, a phobia renders an individuals attention completely incapable of acknowledging anything else and magnifies the feeling of danger with more fear.
Fear can help heighten caution to adopt a safer approach to certain situations, however, it can also prevent us from moving forward, hindering progress. One must understand where fears come from and, if possible, try to face said fears, step by step, and challenge the situations that generate them to be able to live a "normal" life that isn't limited by fear.