When we are facing a dangerous or life threatening situation, our bodies are naturally built to enter a state of alertness. Our heart-rate increases, we start to shake, and we feel nervous or scared. In other words, we experience fear. This alertness prepares us physically in order to either fight the threat, or run away from it . This reaction is not only natural, but also helpful. For instance, if we suddenly see a car quickly speeding towards us while we are crossing the street, we immediately start to run because we fear that it will hit us. In this case, fear saves our life. On the other hand, when we become worried about an issue that will take place sometime in the future, we are experiencing anxiety. Anxiety can also be helpful. For example, if a student is anxious about an exam she/he has the following week, she/he is likely to study hard in order to prepare for it.