Philippians 4:4: Rejoice in the Lord alway; and again I say, rejoice.
Paul was imprisoned in the Roman prison. He was falsely accused and was facing an early death. He underwent shipwreck, was beaten multiple times. Yet in spite of all this, with his hands chained in the prison, he writes to the church at Philippi to rejoice in the Lord always.
How we react to situations in our life brings out the real we. Do we give up hope and go back on God when things fall apart? How do we respond when our first baby dies because he/she was premature? When we lose our job, how do we respond? When somebody cheats on us, how can we still think of praising God? These things are nothing compared to the trials that Paul went through. He had a heart of gratitude to God. He is encouraging us to rejoice in the Lord always. That includes even during our times of distress and hopelessness. God should be our only hope and strength at all times.
God is the strength of our life. Think about His goodness to you at other times of your life and be thankful to Him. If He has taken care of you and provided for you until now, He will still continue caring of you. Let your hearts be glad. Sing for joy. Praise Him because He deserves it.