It is the spirit of fear. Christians who suffer from this satanic agent allow doubt and worry to creep its way into their heart. The same is true of our Christian walk with the Lord. We either do or do not trust Jesus with our life. The Apostle Paul understood the relationship between being a Child of God and that of fear.
Christians can fall into a trap of fear.
We must protect ourselves with the Holy Spirit - freely offered by God to every born again believer. Back to the text we find men building the walls of Jerusalem. When God calls us to a particular work of plan, He does not promise it to be problem free. Let us follow the example of Ezra and the workers on the wall. Stand firm against the attacks of our spiritual enemies and the Lord will grant us ultimate victory.