How does Paul speak of this un circumstantial joy while locked in a Roman in prison? It's because he recognized that God put him there. Paul's joy was not tethered to his comfort. Rather then asking God "why is this happening to me" he asked, "How can I be a part of what God is doing here?" So If you want joy that isn't tied to your circumstances, pray like Paul... "Lord use me today, my life is at your disposal."

Paul writes to a struggling church and encourages them that God is at work in them in the midst of their hardship. He urges them to see beyond circumstances, to move towards one another, and trust that God is going to finish what he started.