Two armies stood in array on separate hills opposite each other and at the ready. The only thing between them and massive carnage lay a valley. Unbeknownst to either side, the invisible enemy of both stood in the center of the valley, egging on the generals of each army.
v4 And there came out from the camp of the Philistines a champion named Goliath of Gath, whose height was six cubits and a span.
v24 All the men of Israel, when they saw the man, fled from him and were much afraid.
v32 And David said to Saul, “Let no man’s heart fail because of him. Your servant will go and fight with this Philistine.
v33 Saul said to David, “You are not able to go against this Philistine to fight with him, for you are but a youth, and he has been a man of war from his youth.” [1 Samuel 17:4, 24, 32, 33]
“You are not able??” Has the serpent ever told you that you were not able to do something? I know I have heard that voice on my shoulder, many times, and sadly I was not able. Worse yet, I was talked out of it. What was the excuse he used to talk you out of doing something? You’re not smart enough. You’re not strong enough. You’re not good enough. You’re too short, too tall, too heavy, too skinny, too. . . And the list goes on. We can learn something from David, even while he was a young shepherd boy. Here is what David told Saul, “The Lord who delivered me from the paw of the lion and from the paw of the bear will deliver me from the hand of this Philistine .” He picked up five stones, one for Goliath and just in case, one each for his four brothers. He then ran toward the nine foot plus giant and slung his first stone burying it in the forehead of Goliath.
Christ wouldn’t be born for another 980 years  and David had it figured out. What held me back? What’s holding you back. We have Jesus and most of us haven’t figured it out yet. I (we) can do all things through Christ which strengtheneth me (us) . We, me included, let Satan talk us out of too many things. Four words — stop listening to him! In all fairness, it is a process. Start the process now . Literally say this to yourself, I can do ALL things through Christ which strengtheneth me. I just did.
Who or what is the giant in your life? What is holding you back from victory? Lets pray.
“Our gracious heavenly Father, I come to you in repentance asking forgiveness. Many times I have not relied on Jesus to deliver my giants into my hands. Throughout your Word and more times than I can count, you have delivered giants unto the hands of your people. Many things in my life have seemed insurmountable and yet many times I have neglected on calling on you. Lord, you stood at the ready and I by-passed you. I either didn’t try because I thought I wasn’t able, or I tried to do them on my own. On both counts, Lord, I failed, and I ask your forgiveness. I worship you and thank you Lord for never leaving me or forsaking me. Lord, you are Jehovah-Shammah and are always there. Lord, I’ll do my best to be at the ready and be your warrior and Watchman in these days. Lord, I pray for my brothers and sisters in you, that you will deliver their giants into their hands. Help their unbelief like you did for me Lord. Your Word says that the fields are white unto salvation. Send them into our hands, Lord. And like Gabriel said in the movie bearing his name, “Just one more, Lord. Just one more.” I pray this in your precious name, AMEN.”
You can find the story of David  and Goliath in 1 Samuel 17. 
 1 Samuel 17:37
 A biblical generation was 35 years and there were 28 generations between David and Jesus
 Philippians 4:13 KJV
 James 4:17; Luke 12:35; John 9:4; Proverbs 14:23; Proverbs 3:28; Proverbs 5:23; Colossians 4:5. Today is the first day of the rest of your life. A journey of a thousand miles begins with a single step. Don’t let the grass grow under your feet.
 A cubit is 18″ and a span is 9″