When I have a difficult decision to make (especially one about ministry), I almost always ask other people for their input. Now to be fair to David, this passage doesn't say that he asked for his men's input; they just give it to him. However, their input does cause David to doubt. He'd clearly heard from God about what he was supposed to do, but when he heard others' objections, he went back and asked God what he should do. In this passage, God just gives him the same answer a second time. (I'd love to know the tone of verse 4--Is God patient with David's fear? Is God irritated and frustrated to be having this conversation a second time?) Then David does what God told him, and he is of course successful.
This is a struggle for me, because God often uses other people to help guide and direct me. But David's men were motivated by fear, and were therefore not objective advisors. They were not seeking God's direction at the moment. Oftentimes the people I seek advice from are somehow emotionally connected to the issue, namely because they're emotionally connected to me. Yet this passage reminds me that if I've heard from God, I must stay true to that direction, regardless of my loved ones' objections.

1 Samuel 23:1-5 and 1 Samuel 23:20-21