We know for sure that Paul is in prison during this writing. Keep that in perspective as you read Philippians. Paul is struggling with his imprisonment and he is going to tell us what his remedy is for fear, which I believe torments human existence. Paul is also going to tell us by eliminating fear in your life, here's what you can expect to happen. Keep the idea in your mind that he is in prison, he's dealing with the concept of fear and how if you can manage fear how it changes your life.
Short Outline of the Book of Philippians from the Today's English Version: