The following is a re-post of a blog by Mark Batterson:
First, God-confidence is a byproduct of humility. The more your humble yourself before God the more favor you expect. It sanctifies your expectations and it builds a holy confidence that God is in control. Humility is the way we stay out of the way of what God is doing. Holy Confidence is confidence that finds it's locus in Christ alone. The confidence for salvation. The confidence of favor. The confidence for miracles. The confidence for grace.
Second, God confidence is the byproduct of authority. We grossly underestimate the authority that is ours by virtue of the fact that we are "in Christ." He has given us "all authority." As long as we are functioning in the will of God, all things are possible. If that doesn't give you confidence nothing will.
Humility + Authority = Holy Confidence.