It's not bad to have fear, depending on what your fear is.  The problem is that most people fear the wrong things.  In the case of the Israelites, they were afraid of what might happen to them if they ended up in Babylon.  So instead of fearing God (which is whom they truly should have been afraid of), they feared the king of Babylon.  The result?  They died.  God had a plan for them that was communicated through Jeremiah: don't run away to Egypt and trust in the Egyptian king.  They chose to ignore that and faced the consequences.  So often we can be afraid of doing what God calls us to do when it is, in fact, the best thing for us.  Fear of something or in someone other than God really can be debilitating to us if we don't place our ultimate trust and fear in Him.  What are you doing to combat fear?  Is your fear properly placed?