"But Moses said to God, 'Who am I that I should go to Pharaoh and bring the children of Israel out of Egypt?' He said, 'But I will be you, and this shall be the sign for you, that I have sent you when you have brought the people out of Egypt, you shall serve God on this mountain.'" - Exodus 3:11-12, ESV
God missed his opportunity to build up Moses' self-esteem. Here God has called Moses to the greatest liberation "project" ever. God tells Moses that he is going to send him to the Pharaoh in order that he might bring God's people out of Egypt. Moses' first response: "Who am I that I should go to Pharaoh...?" Can you see the self-esteem of Moses not registering on the esteem gauge? Moses does not believe that he is able to accomplish this great task. As he said, "Who am I," I can picture his head drifting downward as if in total self-defeat.
Moses is feeling horrible about himself. God has the perfect opportunity to build Moses up. He has the opportunity to encourage Moses, telling him that he can do anything that he sets his mind to. He can pump him up for "game time", telling him how vital and valuable he is on the team. And God's first words are, "But I will be with you..." In other words, God says, "You're right, Moses. You can't do this."
We are called by God to go. He sends us out, but he promises to be with us. Our goal is not to accomplish but rather to obey. We are called to trust rather than take control. We are sent out by a God who knows our weaknesses and insecurities, and yet he still sends us. And the main thing we are to hold on to in our discouragements, battles with low self-esteem and doubts is this: God is with us. We focus on God, not on ourselves.
So when you stand there explaining to Jesus why you just can't do what he is sending you to do, maybe instead of imagining him telling how amazing you are, you should start with the fact that GOD IS WITH YOU. Anything about you after that truth just doesn't matter. Remember: no matter how many you face, you plus Jesus is ALWAYS the majority.