1 Samuel 17:32-58

"'Don’t worry about this Philistine,' David told Saul. 'I’ll go fight him!'
'Don’t be ridiculous!' Saul replied. 'There’s no way you can fight this Philistine and possibly win! You’re only a boy, and he’s been a man of war since his youth.'
But David persisted. 'I have been taking care of my father’s sheep and goats,' he said. 'When a lion or a bear comes to steal a lamb from the flock, I go after it with a club and rescue the lamb from its mouth. If the animal turns on me, I catch it by the jaw and club it to death. I have done this to both lions and bears, and I’ll do it to this pagan Philistine, too, for he has defied the armies of the living God! The LORD who rescued me from the claws of the lion and the bear will rescue me from this Philistine!'
Saul finally consented. 'All right, go ahead,' he said. 'And may the LORD be with you!'" v.32-37
Criticism couldn't stop David. While the rest of the army stood around, he knew the importance of taking action. With God to fight for him, there was no reason to wait. People may try to discourage you with negative comments or mockery, but continue to do what you know is right. By doing what is right, you will be pleasing God, whose opinion matters most.

To fight like David we need David's kind of fearlessness. David had grown strong in his confidence by trusting God when he had encountered wild animals while guarding his father's sheep. When you face towering problems, recall how God has helped you in the past. Take heart because God gives you strength. Use the skills God has already given you and move forward.

Taken from the NLT LIfe Application Study Bible