The letter to the Philippians is a friendly, compassionate, and family type letter. Paul does not present himself as an apostle but as a servant. The church in Philippi might be could be considered as the church Paul was closest to.  

In this letter Paul does his best to address the mindset of the Philippians by sharing his own mindset on how he lives in all circumstances. He has a mindset on suffering and on joy. This mindset is dominated by his aspiration to pursue Christ, to gain Christ and to have Christ the reason for living. By sharing his mindset he is trying to help the Philippians (and us) have the same kind of mindset.