Our joy, prayers, and thankfulness, should not fluctuate with our circumstances or feelings. Paul was not teaching, in 1 Thessalonians 5:16-18, that we should thank God for everything that happens to us, but in everything we should give thanks. Evil does not come from God, therefore, we should not thank him for it. However, when evil strikes, we can still be thankful for God’s presence and for the good that he will accomplish through the distress.  I know good will accomplish something good through our lives.