First Letter to the Corinthians 1,26-31. 
Consider your own call, not many of you were wise by human standards, not many were powerful, not many were of noble birth.
But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong;
God chose what is low and despised in the world, things that are not, to reduce to nothing things that are,
so that no one might boast in the presence of God.
He is the source of your life in Christ Jesus, who became for us wisdom from God, and righteousness and sanctification and redemption,
in order that, as it is written, ‘Let the one who boasts, boast in the Lord.’

Paul tells us that to understand God's work we have to reflect on our call. We are weak, we are often considered mad because of Christ, we are not rich... but God chose us, because he needs only that we surrender to Him and that we let Him manage everything. He needs only that we turn to Him, by participating to the Eucharist and by offering our life and His life for the redemption of the world.