But now your kingdom will not endure, because you have not kept the Lord’s command

1 Samuel 13:1-23
The Philistines assembled to fight Israel, with three thousand chariots, six thousand charioteers, and soldiers as numerous as the sand on the seashore. They went up and camped at Mikmash, east of Beth Aven. When the Israelites saw that their situation was critical and that their army was hard pressed, they hid in caves and thickets, among the rocks, and in pits and cisterns.
Saul remained at Gilgal, and all the troops with him were quaking with fear. He waited seven days, the time set by Samuel; but Samuel did not come to Gilgal, and Saul’s men began to scatter. So he said, “Bring me the burnt offering and the fellowship offerings.” And Saul offered up the burnt offering. Just as he finished making the offering, Samuel arrived, and Saul went out to greet him.
“You have done a foolish thing,” Samuel said. “You have not kept the command the Lord your God gave you; if you had, he would have established your kingdom over Israel for all time.  But now your kingdom will not endure; the Lord has sought out a man after his own heart and appointed him ruler of his people, because you have not kept the Lord’s command.”
 Not a blacksmith could be found in the whole land of Israel, because the Philistines had said, “Otherwise the Hebrews will make swords or spears!” So all Israel went down to the Philistines to have their plow points, mattocks, axes, and sickles[f] sharpened Saul musters his troops and waits seven days, during which time the army steadily dwindles(不斷減少). But he fails to see the seventh day out. And his disobedience and arrogance in taking over the function of the prophet cost him his dynasty.
Why?
Samuel won the Philistines by the Lord, the situation between Israelites and Philistines are the same. No iron weapon, and no enough soldiers in Israel.
Saul did not obey the command of the Lord, so his dynasty ends. 
Victory is no by men or horse but by the power of the Lord.
Be aware that God is my fortress and my savior, follow God's command is the best way to get the victory. 
How?
Obey God's command and follow the way of Jesus is the way to joy and peace.