Rejoicing always

At least some part of Paul's final exhortations to the church in Thessalonica is quite challenging; especially the one in 1 Thess 5:16-18. 'Rejoice always, pray without ceasing, give thanks in all circumstances; for this is the will of God in Christ Jesus for you.' Though challenging, we cannot run away from it, because we are bound by it. It is the will of God for us, or what God demands from us.
Is it possible to 'rejoice always'? There are circumstances in life, actually most of the time, which drives us to sadness and sorrow. Everyone goes through disappointments, sorrow, and sadness even though for brief periods. Though the good Lord may spare us for long and deep valleys of depression, rejoicing always includes those brief periods as well. 
Rejoicing always, in spite of long and short spells of sadness is possible only if we take it as the command of God. It is not a suggestion but imperative on us. We are under order to rejoice! We have no choice other than being joyful in spite of all the adverse circumstances. 
Rejoicing always is a major theme of Paul's life. His life was full of tragic and challenging experiences: hardships of life, imprisonments, ailments, opposition. However, he kept his life in Christ upbeat.
Paul penned the advice 'rejoice, rejoice and again I say rejoice' (Phil 4:4). This often-quoted Bible verse was written in prison as most scholars agree. However, we have much more concrete evidence in the Book of Acts (Acts 16:25-33). When Paul and Silas were shut behind the bars in the city of Philippi they did not spend the night planning a jail-break. But they were praying and singing. What kind of songs were they singing? Luke, the writer of Acts is clear that they were not singing a song for deliverance but they were singing hymns to God. Hymns are songs that adore God. In the midst of their suffering, physical and emotional hurt, humiliation and imprisonment they were not thinking of freedom and justice but of the glory of God. 
For a godly man like Paul, rejoicing always came very naturally. Thus he has the right to write that it is the will of God for us to do the same. But from my experience, I can only say that that is still an art that I am yet to master.