Who Set Their Mind on Earthly

In my recent post "A question of citizenship" I shared my struggle of how to know what it means to be in the world but not of it. Philippians 3 speaks volumes on this subject. I've pulled up the following word study on this passage.
Philippians 3:18-21
18 For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ: 19 whose end is destruction, whose god is their belly, and whose glory is in their shame who set their mind on earthly things. 20 For our citizenship is in heaven, from which we also eagerly wait for the Savior, the Lord Jesus Christ, 21 who will transform our lowly body that it may be conformed to His glorious body, according to the working by which He is able even to subdue all things to Himself.
The New King James Version. 1996, c1982 . Thomas Nelson: Nashville

My principle point of interest is the clause "who set their mind on earthly things"- Paul calls the people who do this the enemies of the cross of Christ. Obviously, this is a serious matter. The Greek verb that encompasses the words "who set their mind" is the word 'phroneo' meaning to mind. Generally it means to entertain or have a sentiment or opinion; by implication to be (mentally) disposed (more or less earnestly in a certain direction); to interest ones self with concern or obedience, to set affection on. Specifically for Phil. 3:19 it means moral interest or reflection, not mere unreasoning opinion. What exactly what does this mean for us? The words used here seem to indicate whole hearted, single-minded love for the world. Matthew Henry says this on the subject "[those who mind earthly things]relish earthly things, and have no relish of the things which are spiritual and heavenly. They set their hearts and affections on earthly things; they love them, and even dote upon them, and have a confidence and complacency in them." (emphasis mine)
It seems to me that this verse is talking about those who love the world and the things in the world firstly. Not those who are in the world, maybe even involved in the things of this world but who put Christ first. The former can be played out in a number of different ways. It may be as 'big' as putting ones allegiance to one's country ahead of allegiance to God, or it may be as 'simple' as watching a movie instead of studying God's word on a regular bases. But to me one thing is quite clear: this verse is not suggesting total apathy and separation from the world. Paul urges the Corinthians not to stop working to wait for the return of the Lord. Jesus tells us to "go into all the world and preach the gospel." These passages hardly support separation from the world, but more a separation of affection for the things of the world. Our focus, our desire, our passion should be for God and God alone and this should shine through in whatever we do, whether we are in politics or business, our focus should be on Heaven "From which we also eagerly wait for the Savior, the Lord Jesus Christ, 21 who will transform our lowly body that it may be conformed to His glorious body..."