God usually likens His children to an animal or inanimate objects to drive a salient point home and establish faith in our hearts. He had likened His people to an eagle, sheep, etc. Likewise, God compared Jeremiah to an Iron that will be unbeatable and unconquerable. So also, God likened Simon Peter to a stone to instil firmness in him.
Jeremiah was afraid, first because he was a child and was wondering if he was fit for the work God had assigned him to do. Second, Jeremiah knew the people God sent him to were wicked and did not want to accept the truth. Had God given him an option to decide, he would have opted out for fear of facing a hostile people.
Put Your Confidence in God
Similarly, we often think we are too small for the task ahead of us, or our vision seems too big to handle. And on the other hand, it could be the fear of failure, a past horrible experience, or because enemies embattle us, and they are doing everything to hold us back or destroy us.
This is the word of God to you; God is saying He has made you an unbendable and unconquerable iron, and the best reaction should be to trust Him. The usual saying that one with God is the majority is not a fallacy but the truth. Put your confidence in God, and you shall be victorious.
If the early pilgrims in the journey of faith did not die in their battle but had their strength renewed daily as they trusted God. You, too, will be victorious if you do what they did by trusting God.