David was a leader who was confident. But not a self-centered trust, but trust in God: «With your support I will launch myself against an army; with you, my God, I will be able to assault walls ”(v.29). David recognizes that he needed God to:

Protection
"Shield is God to those who take refuge in him" (v.30b) "You cover me with the shield of your salvation" (v.35).

Strength
«It is he who arms me with courage and straightens my path; It gives my feet the lightness of the deer, and keeps me firm in the heights ”(vv. 32–33).