We will not win the victory if we fight in our own strength. We must draw our strength from the Lord.

1 Samuel 17:1-58 
David defeats Goliath. This is not only a story about David and Goliath. It is about the Israelites and the Philistines. It is about 'God' and the 'gods' (43,46). Victory comes from the Lord. It is given by grace. It is received by faith (47). Notice the contrast between the attitude of Saul - unbelief -and the attitude of David - faith (33,37). Unbelief is all around us. Don't be pulled into it. Don't forget God. Remember what He has done for you and thank Him that He will not fail you now (37). Put off the armour provided by men. 'Put on the whole armour of God' (38-40; Ephesians 6:11). We will not win the victory if we fight in our own strength. We must draw our strength from the Lord. He helps us. We are 'strengthened with might through His Spirit in the inner man' (Psalm 121:2; 124:8; Ephesians 3:16).