As I was reading I Samuel 18, it constantly used the term afraid when it was talking about King Saul. Let me set the scene for you.
David has just killed Goliath and all of the women are singing his praises. Okay men that was a pretty cool moment wasn't it? Then King Saul begins to be afraid that David is going to take the kingdom away from him. Wasn't it already prophesied that God would give the kingdom to another? Seems like to me you can't be afraid of losing your position as long as God has put you there, and you can't change God's mind about moving you on. So, if you are in this situation maybe you should remember that God is in charge. Okay back to the story. King Saul is so enraged that he asked (read forced) David to play the harp for him in the throne room and then he tries to kill him with a spear. Now listen to what the Bible says next in verse 12 "Now Saul was afraid of David because the Lord was with him..." That seems strange to have fear and the Lord in the same sentence doesn't it? But maybe we can get some more information as to why Saul was afraid. Look at the last part of verse 12 "...but had departed from Saul." Now that is a reason to be afraid.
Saul saw the presence of God on the life of David and he was jealous because he remembers what it was like to enjoy the presence of God. Who can you most identify with today, Saul or David? Are you afraid because you are without the Lord, or are like David ready to do whatever the Lord says?
Whether you are most like Saul or David the good news is that you can always come to God and know that He will cast out all of your fear.