Summary: As Christians, we get sucked into the ways and wants of this world and we forget where are true home lies because our citizenship is is heaven. We are are only passing through this world.
With our modern GPS’s, on most of our smart phones, we can get to where we want to go, only if we correctly put in the correct co-ordinance, or the right address.
A Swedish couple on vacation near Naples, Italy. They want to drive to the very scenic and romantic holiday isle of Capri located in the Gulf of Naples. Instead they drove to Carpi, an industrial town in northern Italy, because they misspelt the name in their car's GPS. Italian officials say the couple asked at Carpi's tourist office where they could find Capri's famous Blue Grotto. The car's GPS system had sent them 650km (400 miles) off course to Carpi. "Capri is an island. They did not even wonder why they didn't cross any bridge or take any boat," said a bemused tourism official in Carpi. Once they realized their mistake, the couple got back in their car and headed south, the official added. 
How many Christians lose sight of their destination. It is not that we forget who we are, but we forget Whose we are.
The key idea to today’s message is do we know to whom we belong? Where is our true home? Paul reminds the church in Philippi:
Philippians 3:20a (NKJV) For our citizenship is in heaven
What is interesting about this is the context in which Paul is reminding them. Philippi is a town full of military retirees. Sound familiar? It's like our town of Niceville Florida, we're full of military retirees. I, myselfe have retired from the military after 25 years of service. In 30 BC the Romans starting populating Philippi with retired soldiers. They were full fledge citizens of Rome and the their land was considered a little piece of Rome. As Roman citizens, they enjoyed all the privileges of Rome without actually being in Rome. They payed no taxes and they had all the rights of a Roman citizen. They understood Paul when he wrote that their citizenship was in heaven, a far away place, while they lived in a foreign land. Peter said in his letter to those who were being persecuted:
1 Peter 2:11 (NKJV) Beloved, I beg you as sojourners and pilgrims, abstain from fleshly lusts which war against the soul
"Sojourners and pilgrims.' Our stay here in this world is temporary. We are only passing through. Our home is with Jesus. This world is not our home. This is a difficult concept to understand when this world is all we know. We must understand where we are going and that in this world, we are only passing through.
My son Bobby and His wife currently live in Singapore, quite literally halfway around the world from where we are in the panhandle of Florida. They have lived there since 2010. Their daughter, Lindsay, was born in Singapore in September 2012. This September she will be 6 years old. She speaks almost as much Chinese as she does English (even though english is the official language of Singapore). Lindsay has never been in the United States. Yet, as soon as she was born, my son Bobby, applied for and received an United States Passport for her. You see, Lindsay is a full-fledged American Citizen even though she was not born here. This October, when they come to visit us, this will be the first time Lindsay has been in the country in which she hold citizenship. Is she any less a US citizen because she has never lived here?
When we travel internationally, we carry a passport, to tell the world, whose citizens we are. Back in Philippi, newborns to these Roman citizens, had their babies names entered into the official register. Likewise, new believers, those who have been born-again in Christ, have their names written into the Book of Life. The Book of Life is the official citizen register of heaven. This Book is serious business, its no joke.
Revelation 20:15 (NKJV) And anyone not found written in the Book of Life was cast into the lake of fire.
Whose Passport do you carry? Where is your home country? Jesus when He prayed to His Father the night before he went to the cross, explained how we are in the world but not of the world.
John 17:14–16 (NKJV) I have given them Your word; and the world has hated them because they are not of the world, just as I am not of the world. 15 I do not pray that You should take them out of the world, but that You should keep them from the evil one. 16 They are not of the world, just as I am not of the world.
If we are not of the world, we have been forgiven, we have been made clean, we are a new creation before God, we aught not to be living as citizens of heaven? But why do many Christians talk, live, and conduct their business as if this world is their home?