in the passage above, Eliab, David's oldest brother, accused him of being conceited (v. 28)
to which David simply turned away to someone else and brought up the same matter (v.30)
Was David conceited or confident? Conceit or confidence depends on whom you place your trust in.
Based upon David's testimony (v. 34-37) and his conversation with Goliath (v.45), David knew the battle is the LORD's! (v. 47) "David revealed the source of his confidence—it was not in experience or the king's armor or his brother's approval. It was in the Lord."
The difference between conceit and confidence is the source of the trust. All believers should have confident in their Lord's ability to deliver them. This may appear as conceit to the world!
"No one took David seriously, not Eliab or Saul or Goliath. But David's confidence wasn't based on the approval of others. Where do we find our confidence? Do we trust our own resources, or our shining resume, or our bank account? Do we seek approval from others, or rest secure in our knowledge of God? We will all face challenges in life, moments when we are asked to stand for what is right. To the world, we might appear insignificant. But God can use even one person willing to be courageous for Him. "