God will always supply the resources we need. When we have a deep relationship with God, our conversations lead us to an honesty about our weaknesses in comparison to God's glory. Jeremiah recognized that he had a shortfall in experience and ability to speak, but these were not hurdles to God. In fact, it seems that God -- to cite a saying -- usually doesn't call the qualified, but, rather, qualifies the called. God was the one who put words in the mouth of Jeremiah, and God will be the one who ensures that the mission is a successful one, even if it will cost a lot in the process.
Some of the most powerful words in the Bible are the repeated promise of God: "I am with you." We have an assurance that the God who calls us will continue to be in conversation with us, and he will continue to lead us. Those conversations are the ones that we need to review often as we follow God wherever God leads.
After all, God always recognizes our voice -- no strings attached.