1-Samuel 4-7

Israelites went into the battle against Philistines, but they were badly defeated.  They then decided to bring the ark of covenant of the Lord into the battle "As soon as the ark of the covenant of the Lord came into the camp, all Israel gave a mighty shout, so that the earth resounded...the Philistines were afraid" (Ch.4 verse 5-7)

Ark of covenant was also accompanied with two of Eli's sons, Hophni and Phinehas, when Israel went into battle with Philistines again, two sons of Eli's were killed in one day and Philistines took the ark of covenant, and defeated Israelites.  

One messenger ran back to Shiloh were Israelites took the ark of covenant from, and told everyone about their great defeat and that they lost the ark of the Lord. He told Eli about his two sons and the ark of the Lord "As soon as he[messenger] mentioned the ark of God, Eli fell over backward from his seat by the side of the gate, and his neck was broken and he died... He had judged Israel forty years." (Ch. 4 verse 18)

Phinehas's wife was pregnant and when she heard of the ark of God she gave birth and named her son "Ichabod, saying,"The glory had departed from Israel... for the ark of the God has been captured" (Ch. 4 verse 21) and died.

Philistines put the ark of covenant into a temple they had for their god Dagon. When the people woke up on the next day they saw that " Dagon had fallen face downward on the ground before the ark of the Lord." (Ch.5 verse 3) So they put Dagon back up on his seat, but the next day they found Dagon down on the ground again but now he was broken in pieces, and Philistines sent the ark of God to a different city.

Everywhere the ark of God was sent "Hand of the Lord was against the city, causing a very great panic, and He afflicted the men of the city, both young and old, so that tumors broke out on them" (Ch. 5 verse 9)

All Philistines were either dyeing or getting these painful tumors. Finally Philistines called their priests and the diviners and asked them what to do with the ark of God how to return it back to it's origin. The priests and diviners said for them to bring the guilt offering to God and set the ark on the carriage. "Then send if off an and let it go its way and watch. If it goes up on the way to its own land to Beth-shemesh, then it is He who had done us this great harm... and the cows went straight in the direction of Beth-shemesh" (Ch.6 verse 9-12)

The ark of covenant of God arrived at field of Joshua at Beth-shemsh, Israelites were happy and they sacrificed the two cows. But "He struck some of the men of Beth-shemesh, because they looked upon the ark of the Lord... and the people mourned " Who is able to stand before the Lord, this holy God?"" (Ch. 6 verse 19-20) 

They asked the people from Kiristh-jearim to come and get the ark of God.  "And the men of Kiriath-jearim came and took up the ark of the Lord and brought it to the house of Abinadab on the hill." (Ch. 7 verse 1) The ark stayed there.

Samuel said to Israel " If you are returning to the Lord with all your heart, then put away the foreign gods and the Ashtroth from among you and direct your heart to the Lord and serve Him only, and he will deliver you out of the hand of the Philistines." (Ch.7 verse 3)

Samuel was praying to God for His protection and security, and he brought an offering to God and God heard Samuel and " The Lord thundered with a mighty sounds that day against the Philistines and threw them into confusion, and they were defeated before Israel. And the men of Israel went out from Mizpah and pursued the Philistines and struck them as far as below Beth-car." (Ch. 7 verse 10-11)

Today...
Ark of Covenant was the presence of the Lord in the days before Jesus Christ. People who were His could withstand this Holy Presence people who were far away from the Lord in their hearts couldn't handle the Holiness of the ark.

At this day and age we have the grace of Jesus's Christ's blood which allows us to be close to God and not perish.

Even when the ark of God returned to Israel in the field of Joshua in the city of Beth-shemesh even those people who were calling themselves a part of God's nation couldn't handle the holiness of the ark.
By "handle the holiness" I mean to do what God had commanded to do and not overstep God's boundaries.

Back then if you were doing something wrong you would be punished with death or with severe illness and you would know that you've done something wrong, but today it could be vague what is right and what is wrong.

How does one know that you're wrong and how to turn to God?
-To know and feel that you're out of  God's territory the Holy Ghost will tell you that something is not right.
-To get back to God, Samuel called all the Israel and said for them to:
1. Turn away from idolatry
2. Direct your heart to the Lord
3. Serve Him alone

These are quite simple, but tough. Turn away from idolatry, meaning there should be nothing more valuable to us that Jesus Christ and pleasing Him.
 Direct your heart to the Lord means that you must take your heart out of everything that wasn't according to God's word, and direct it only towards the Lord.
Serve Him alone, means that we no longer serve our flesh and our desires but we serve God.