Christian Joy is a fruit of the Spirit and it is not the same as Happiness as defined and desired by the world.
The Scripture described Joy as gladness in the heart in anticipation of something great while the dictionary defined Happiness as a satisfying or pleasurable experience.
Joy is such that even when one is in need, or in pain, or in the middle of a storm in life, he can still have joy. Joy does not depend on circumstances and is permanent. Unlike Happiness which depend on circumstances and is fleeting due to the vagaries of life.
A Christian, who truly loves the Lord and obeys His commands to bear the marks of a disciple, will surely experience joy and will not oscillate between happiness and sadness because his family, self and possessions do not have any hold on him and are all surrendered to our Lord. Luke 14:25-35.
For the kingdom of God is not a matter of eating and drinking but of righteousness and peace and JOY in the Holy Spirit. – Romans 14:17.
Count it all JOY, my brothers, when you meet trials of various kinds, for you know that the testing of your faith produces steadfastness. And let steadfastness have its full effect, that you may be perfect and complete, lacking in nothing. – James 1:2-4
“Blessed are you when others revile you and persecute you and utter all kinds of evil against you falsely on my account. REJOICE and be glad, for your reward is great in heaven, for so they persecuted the prophets who were before you. – Matthew 5:11-12
So also you have sorrow now, but I will see you again, and your hearts will REJOICE, and no one will take your JOY from you. – John 16:22
In this you REJOICE, though now for a little while, if necessary, you have been grieved by various trials, so that the tested genuineness of your faith – more precious than gold that perishes though it is tested by fire – may be found to result in praise and glory and honor at the revelation of Jesus Christ. – 1 Peter 1:6-7
Therefore, since we are surrounded by so great a cloud of witnesses, let us also lay aside every weight, and sin which clings so closely, and let us run with endurance the race that is set before us, looking to Jesus, the founder and perfecter of our faith, who for the JOY that was set before him endured the cross, despising the shame, and is seated at the right hand of the throne of God. – Hebrews 12:1-2
Let us REJOICE and exult and give him the glory, for the marriage of the Lamb has come, and his Bride has made herself ready; – Revelation 19:7