Fear that it will not work. Fear is like a rope which Satan uses to tie us down. Fear causes us to focus on what Satan is doing or can do. Fear is the opposite of faith. Faith causes God's power to work on our behalf.
Fear stops it.
We should resist fear just like Moses did. The halfhearted approach. Let your little ones also go with you. For we must take some of them to serve the LORD our God, and even we do not know with what we must serve the LORD until we arrive there. If we are to serve and worship God properly it will involve sacrifice on our behalf.