Joy is not just an emotional state of being, it is a behavior.  As Christians, we can, and we should, exhibit joy in life.  Rejoicing in the Lord is a demonstration that we are allowing the Spirit-revealed Word of God to guide us.  This is why Paul referred to joy as a fruit of the Spirit (Galatians 5:22).

The truth is joy is not only a blessing for the child of God, it is a responsibility.  When we allow ourselves to dwell in depression and mope around in misery, we are giving Satan the advantage.  There is nothing more un-Christ-like than to have a gloom and doom mentality.  God, instead, wants us to rejoice in the Lord (John 15:11).

We should behave the same way Paul did in the house of God.  He did not allow the circumstances of his life to determine his state of mind.  He knew what a blessing it was to be a Christian; thus, he rejoiced even when he found himself a prisoner for the Lord, and he exhorted the brethren at Philippi to follow his example.

Philippians 4:1, 4 (ESV)
¹  Therefore, my brothers, whom I love and long for, my joy and crown, stand firm thus in the Lord, my beloved…⁴  Rejoice in the Lord always; again I will say, rejoice.

Paul rejoiced because he knew his position in life, not physically, but spiritually.  He realized that no matter where he was in this world, spiritually he was in Christ, along with all the saints (Philippians 1:1, 26).   There is no better place to be than in Christ, for that is where we have reconciliation with God.

2 Corinthians 5:18-19 (ESV)
¹⁸  All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation; ¹⁹  that is, in Christ God was reconciling the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation.

To be reconciled to God means that we have gone from being his enemies (sinners) to being his friends (we now have fellowship with Him).  It does not matter what we did in our past, our friendship with God has been restored.  In the past, Paul made havoc of the church, being a blasphemer and persecutor of saints, but he knew that in Christ he was a new creation.  So are we, and, like Paul before us, we should rejoice.

Paul rejoiced, not only because of his present position, but also because of his future prospect.  Paul had his eyes on things eternal.  He said that he was looking, “not to the things that are seen but to the things that are unseen” (2 Corinthians 4:18).  The unseen things he was referring to were the rewards of heaven, including being in the eternal presence of Christ (Philippians 1:23).  The present persecution that he suffered did not stop him from being filled with joy because he knew they could not compare to the glory that awaited him (Romans 8:18).

Our position and prospect are the same as Paul’s; thus, we too should rejoice.  What kind of behavior should people see in us as members of the house of God?  They should see us, not overwhelmed by the circumstances of life, but filled with joy because of the hope that is in us. 

As you wind down for the night, think about these things.