Fear is usually described as an emotion or feeling, and in certain aspects that is true. However, God looks at things at an even deeper level - the spiritual. While fear has feelings associated with it, its roots are not in the emotional but the spiritual. If emotions can be called feelings, then the spiritual realm deals with beliefs. God always deals with the root issues and not just their symptoms. The underlying cause of fear is putting our faith in the possibly negative power of people and circumstances rather than in the goodness of God. There are several root issues that cause us to do this. When we continue in sin without repenting, it is very hard if not impossible to simultaneously have faith in God.
There are binary aspects to the spiritual, and this is one of them. Peeling back the layers, we can see that underlying sin is the desire of man to be in control instead of God. This goes all the way back to the garden of Eden (Gen 3:1-7). The serpent convinced Eve that she could make her own evaluations of good and evil without God. The results were devastating, including the first time people experienced fear (Gen 3:8-10). Adam said he was afraid when he heard the voice of God. The fear of the Lord is the beginning of wisdom (Prov 9:10), and it is the only healthy fear, but the fear Adam was experiencing was the kind of fear that drives us away from God instead of towards Him. It is the fear that God is rejecting and judging me because of my sin, not the fear of being separated from Him which leads us to repentance (2Cor 7:10).
This kind of fear leads to irrational, emotional responses and decisions. There are many examples in the Bible and in our own lives. Lot was Abraham's nephew, but through some poor decisions he ended up in the city of Sodom which was facing destruction because of their abominations (Gen 18-19). Abraham prayed for mercy, and God sent two angels to deliver Lot and his family. The angel told him to flee to the mountain, but he said he was afraid to go there. Why would he be afraid to go where God was sending him in His mercy to deliver him? It is illogical. However, the angel consented to spare a nearby city that was going to be destroyed so he could go there instead. After Sodom was destroyed, Lot was afraid to stay in that city, so he went into the mountain he was supposed to go to in the first place. This is how fear can override faith and sound logic.
When Manoah realized that he and his wife had been talking to an angel of the Lord and not just a man, he thought God was going to kill them for it (Jud 13). His wife asked him why an angel would appear to them to show them that they were going to have a child that would be a judge to Israel if He was just going to kill them. After Babylon conquered Judah, they appointed a man named Gedaliah to govern the land (Jer 40-44). There was another man named Ishmael who was a descendant of the kings. He gathered a group of men and killed Gedaliah and his supporters. Some Jews from nearby cities came to pray and sacrifice to God, but Ishmael killed them too and threw their bodies in a cistern that Asa had dug out of fear of Baasha (Jer 41:9). God had given Asa victory over Ethiopia even though his army was outnumbered over 2 to 1 (2Chr 14-15). Later, when Baasha came against him he took treasures from the temple and hired Syria to help him instead of trusting in God. After Ishmael killed Gedaliah and his fellow Jews, he fled to go the Ammonites who were other enemies of the Jews (Jer 41:10 & 15). Then the Jews that were left decided to flee to Egypt. God told them not to go and that He would take care of them if they stayed in the land. He warned them that everything they were afraid of would destroy them in Egypt, but they went anyway (Jer 41:44). They became so spiritually insane that they blamed the judgment for their sin on failing to worship the female idol instead of because of it (Jer 44).
Courage is not the absence of fear. It is facing fear and not letting it override our faith in God and Biblically based logic. The U.S. Navy Seals are one of the most elite fighting forces in the world, yet even they do not teach the absence of fear but rather the decision to not let it freeze them into inaction. Emotions are part of who we are, but we are not to let them be the basis our our decision making. It's faith over feelings, truth over emotions, and obedience to God over irrationality. It is not spiritual to abandon Biblical principles in time of trouble in order to honor emotions. While sometimes faith doesn't seem to make sense to us from our limited, earthly perspective, it always makes sense from God's eternal perspective. Our job is to follow Biblical principles regardless of how it looks naturally or how our emotions feel. Faith is not always devoid of feeling, but it is not based on it. It is based on the eternal word of God. Following it will always lead to the right outcome in the end, and it will always keep us from the insanity of fear.