"I can't do it" - this is the whole point!!
In every class I give the students a memory verse to learn for the next day. To go with the lesson yesterday, I chose 2 Corinthians 4:7: "But we have this treasure in jars of clay to show that this all-surpassing power is from God and not from us." What is the treasure? The Spirit of God and the knowledge of him. And what are the jars of clay? We are. Moses was. Saul was. I am. If we are weak in a certain area, but ask God to provide what we lack, and then go ahead and act, people will see that God is working through us because of our faults, not in spite of them. Even though I'm not the best teacher in the world, if I do my part - preparing for class and showing up every day - God can use that for his glory. Usually only two or three kids come to class, but yesterday three more girls from the church dropped by the school on an errand and decided to sit in the class. Afterwards, one of the girls told me that this idea, this theme, had been running through her mind for several weeks. She said that, although she is a Christian, she has made some mistakes and she and others have been doubting and wondering how God can use her life. We prayed together, and she said that now she knows that God will restore her and use her for his purposes.
Alone, using my own resources, I can't do it. But if I am willing to be used, there is no limit to what God can do through me.
"I can do everything through him who gives me strength." (Phil. 4:13)