I searched the word "joy" at Bible Gateway, restricting it to the Pauline Epistles. Here is what I found, along with a few of my comments on each verse that came up.
1. Romans 14:17
For the kingdom of God is not a matter of eating and drinking, but of righteousness, peace and joy in the Holy Spirit,
Partying brings a kind of "joy." It is only for a brief time, though. The joy that comes as a gift of the Holy Spirit is not like that. That joy is eternal and no one can take it away. No circumstance in this life can rob a believer of the joy that is theirs in Christ. Christian joy also goes along with righteousness and peace.
2. Romans 15:13
May the God of hope fill you with all joy and peace as you trust in him, so that you may overflow with hope by the power of the Holy Spirit.
Real joy comes from God.
3. Romans 15:32
so that by God's will I may come to you with joy and together with you be refreshed.
There is joy found in fellowship with other believers, especially when we go through difficult circumstances together.
4. Romans 16:19
Everyone has heard about your obedience, so I am full of joy over you; but I want you to be wise about what is good, and innocent about what is evil.
Knowing how God has worked in those we have shared Christ with brings joy.
5. 2 Corinthians 1:24
Not that we lord it over your faith, but we work with you for your joy, because it is by faith you stand firm.
The desire of a true shepherd of God is that those under him will have joy. He wants the best for them and wants to work with them. The real spiritual leader doesn't try to boss people around.
6. 2 Corinthians 2:3
I wrote as I did so that when I came I should not be distressed by those who ought to make me rejoice. I had confidence in all of you, that you would all share my joy.
If the Apostle Paul was happy, then they could all be happy. If they were still tolerating sin in their midst, then there would be no joy shared with Paul. True joy from God involves separating oneself from sin. True Christian fellowship is based on the truth. When we "hide" sin among us, there can be no fellowship and no joy.
7. 2 Corinthians 7:4
I have great confidence in you; I take great pride in you. I am greatly encouraged; in all our troubles my joy knows no bounds.
Paul was confident that they would obey God in the things he had written to them about in the first letter. Knowing that made his troubles less and even "worth it."
8. 2 Corinthians 7:7
and not only by his coming but also by the comfort you had given him. He told us about your longing for me, your deep sorrow, your ardent concern for me, so that my joy was greater than ever.
Paul was joyous to find out that the Christians in Corinth had taken care of the problems they had. He was happy to find out that they still loved him even after he had rebuked them strongly. He was glad to see that they loved righteousness and hated sin.
9. 2 Corinthians 8:2
Out of the most severe trial, their overflowing joy and their extreme poverty welled up in rich generosity.
Often those who have the least as far as this world goes are the ones who most understand the joy in giving principle.
10. Galatians 4:15
What has happened to all your joy? I can testify that, if you could have done so, you would have torn out your eyes and given them to me.
False teachers had confused the Christians in Galatia. Because of accepting wrong teachings about the Law, they had lost their joy. False teachings rob a Christian of joy. The Holy Spirit is not in heresy, so His joy is not present, either.
11. Galatians 5:22
But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness,
Again, real joy is from the Holy Spirit and is fruit of His work in our lives.
12. Philippians 1:4
In all my prayers for all of you, I always pray with joy
Paul prayed with joy for those who were his brothers and sisters in Christ.
13. Philippians 1:25
Convinced of this, I know that I will remain, and I will continue with all of you for your progress and joy in the faith,
Growth brings joy.
14. Philippians 1:26
so that through my being with you again your joy in Christ Jesus will overflow on account of me.
Paul was in prison for his faith. They were all suffering because of it. Paul was torn. He would have liked to die and enter God's presence, but he knew that the Christians needed him to continue teaching and encouraging them. His presence with them after being released from prison would give all of them great joy.
15. Philippians 2:2
then make my joy complete by being like-minded, having the same love, being one in spirit and purpose.
Unity among Christians gives us joy.
16. Philippians 2:29
Welcome him in the Lord with great joy, and honor men like him,
Paul was telling the brethren to receive Epaphroditus with joy and honor. He had been willing to give his life for the sake of the Gospel. God had mercy on him.
17. Philippians 4:1
Therefore, my brothers, you whom I love and long for, my joy and crown, that is how you should stand firm in the Lord, dear friends!
Paul, though he was in prison, found joy in knowing that His friends were standing firm in the faith. He longed to be with them. That was all he wanted - to be with them.
18. 1 Thessalonians 1:6
You became imitators of us and of the Lord; in spite of severe suffering, you welcomed the message with the joy given by the Holy Spirit.
Where can one who is suffering find joy? There is joy in the Lord and this joy is given as a gift by the Holy Spirit. When we have nothing left, we still have the joy of the Lord to strengthen and encourage us.
19. 1 Thessalonians 2:19
For what is our hope, our joy, or the crown in which we will glory in the presence of our Lord Jesus when he comes? Is it not you?
When Paul and his companions stood before God, the ones who had come to the Lord through their ministry would be their source of joy. They would not be entering Heaven alone.
20. 1 Thessalonians 2:20
Indeed, you are our glory and joy.
The fact that the believers were going on with the Lord brought Paul and his companions joy.
21. 1 Thessalonians 3:9
How can we thank God enough for you in return for all the joy we have in the presence of our God because of you?
Joyful fellowship in the Lord.
22. 2 Timothy 1:4
Recalling your tears, I long to see you, so that I may be filled with joy.
Paul was sad because Timothy was sad. They were very close, like father and son. Their separation and Paul's difficult circumstances caused them both pain. Paul looked forward to a joyful reunion with his dear friend.
23. Philemon 1:7
Your love has given me great joy and encouragement, because you, brother, have refreshed the hearts of the saints.
Other believers who are an encouragement to us bring joy to our hearts.
Definition of the Greek word "χαρά - chara" which is translated as "joy" in many of these verses:
"1) joy, gladness
a) the joy received from you
b) the cause or occasion of joy
1) of persons who are one's joy"
Blue Letter Bible