Do you know how the Torah describes the first leader of the Jewish people? The man who is described as having spoken with G-d “face to face”; The man who stood up to the mightiest ruler of the world and demanded, “Let my people go!”; do you know how the Torah describes Moses?
As the humblest person on earth.
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 even to argue with G-d, when necessary.
Confidence is best found among the truly humble.
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.