"When I am weak I am strong."

Please listen Tim Keller sermon Who Will Convert the West? - YouTube. 

What kind of people will convert Japan? In Keller's illustration from D. Martyn Loyd-Jones, elderly preachers say concerning a popular young preacher, "I'm not sure he's been humbled yet."

"When I am weak I am strong."2 Corinthians 12:10b

Here's more: Tim Keller - How To Change Deeply - YouTube