First, David was not scared of Goliath because he didn't see him as great. Instead, he saw his God as greater. I thought about how many times I have thought of my problems or fears and allowed them to grow to be so great in my mind, instead of being reminded that my God is and always will be greater than anything I may face. David was also enraged at Goliath because he was blaspheming his God. The one true God. I wonder, if someone blasphemes or my God, do I bow up in anger or do I cower in fear as Saul and the other Israelites did? David also operated out of a position of understanding that God had already promised to defeat his enemies and the victory was decided. The battle was not something to be questioned, avoided or feared, but something to go and be taken. So was David brave, yes, but only because he had the right perspective on the situation and the right viewpoint of God and what it meant to be a child of Him.
So how does this affect my life? Well, I hope it means that I will know what it means to live in a spirit of victory and to never allow my circumstances, problems, or fears to consume or defeat my spirit. That I would understand that I live with the power and strength of Christ who lives in me. The same power and strength that defeated sin, death and the devil himself. That is the strength that lies inside of me. With that, why should I be afraid? With that, what should I fear? The victory has been won by my mighty Savior and in the end, any "battle" he fights for me is all for HIS GLORY.