(2Co 4:7) But we have this treasure in earthen vessels, that the excellency of the power may be of God, and not of us.
God entrusted the precious message of salvation in Jesus Christ to fragile and fallible people. Paul emphasized the inestimable value of the force in the instrument - the Holy Spirit within us. Even if we're weak, God still uses us to spread His Good News, and He provides us with the strength to do so.
The realization that the strength doesn't belong to us, but to Him, withhold our pride and motivates us each day to have fellowship with our Power Supply ... God. It is our responsibility to ensure that people see God in us!