This is one of the underlying themes throughout all of Scripture: despite our own unfaithfulness, God remains faithful. An appropriate response to God's unending grace and generosity is wonder. Peterson contrasts Jesus' words (why hast thou forsaken me?) with our own: why hast thou accepted me?
The Bible teaches that we are born in sin, and will not seek God on our own... yet all are called to repent. How is this possible? The answer is known as 'prevenient grace,' which bridges the gap between what we are able to do and what God calls us to to.