2 Corinthians 12:9 -- But [God] said to me, "My grace is sufficient for you, for my power is made perfect in weakness." Therefore I will boast all the more gladly about my weaknesses, so that Christ's power may rest on me. (NIV)
The thing that you think is holding you back might be the very thing God will use to make great things happen. Can you think of any examples of this from your own life? From the lives of others?