True confidence is best found in those who are truly humble.
Moses was the most humble of all men. Yet he had the confidence to stand before the mightiest dictator on earth and assert his demands. He had the confidence to stand before G‑d and listen without losing his composure. He had the confidence, when necessary, even to argue with G‑d.
Yet he considered himself to be truly nothing.
The confidence of Moses was not confidence in his own self. He had no self. He was but an agent of Above. Above there is infinite power.
Self-confidence is limited, at best. But if you trust in the One who has sent you to be here and do what you need to do—that confidence knows no bounds.
Humility is knowing your place in this life. When you know your boundaries and the space G-d created for you on this earth, then you ask Heaven to come down and fill that space where you must physically dwell for a short time.
With that understanding confidence will grow.
The arrogant are opposite. They try and fill every space where they are not invited with their egos.