Peter

The testimony of Peter's life:

Never hurts to stop and think for a moment before you speak.
Beware of spiritual boasting.
God knows you better than you know yourself.
No matter how egregious your failure the Savior's response is: "Move on. Feed My sheep. I want and need you in the workings of My kingdom." (Don't let anyone tell you otherwise.)
Failure is the bedrock on which God builds faithfulness.
If God needs you elsewhere, jails will not hold you. Kings cannot stop you.
Jews, Samaritans, Gentiles--the gospel is for everyone. Take it to them eagerly.
Defend God's message of grace.
Beware of how subtly legalism can creep back into your walk.
Go where God sends you no matter what others might think.
God can turn a willing vessel from a denier into a dynamic, fearless messenger of the gospel.
Failed? God knows that you love Him.