“And though you have not seen Him (Jesus Christ), you love Him, and though you do not see him now, but believe in Him, you greatly rejoice with joy inexpressible and full of glory.”  1 Peter 1:8

For those who belong to the Lord there is that joy unspeakable and full of glory.  For all of mankind the occasions of great joy (though many will reject them) are:
*The coming of Christ,
“Then the angel said to them, ‘do not be afraid, for behold, I bring you good tidings of great joy which will be to all people.
For there is born to you this day in the city of David a Savior, who is Christ the Lord.'”  Luke 2:10-11

*The resurrection of Christ Jesus:
“So they departed quickly from the (empty) tomb with fear and great joy, and ran to bring His disciples word.”  Matthew 28:8  (My emphasis)  
Read Vs. 1-8 for the whole scene.

*The ascension of Christ Jesus:
“Now it came to pass, while He blessed them, that He was parted from them and carried up into heaven.
And they worshiped Him, and returned to Jerusalem with great joy.”  
Luke 24:51-52 

*The conversion of gentiles,
“So, being sent on their way by the church, they passed through Phoenicia and Samaria, describing the conversion of the Gentiles; and they caused great joy to all the brethren.”  Acts 15:3

I suggest that you read the above verses in context for the joyful blessing they give.

We who are covered over with the righteousness of Christ know the joy of that new life in Christ.  Isaiah, in 61:10, is speaking of the Church who we are,
“I will rejoice greatly in the LORD
 My soul will exult in my God;
 For He has clothed me with garments of salvation,
 He has covered me with the robe of righteousness,
 And as a bride adorns herself with her jewels.”  

We rejoice because we are the Lord’s and He loves us with an everlasting love.  He is in control!  Knowing this, there is that peace in our innermost being no matter whatever the circumstances.  And where there is that peace, joy is inevitable.

Jesus gave us His peace and His joy, neither depends on circumstances!
“Peace I leave with you; My peace I give to you; not as the world gives do I give to you.  Let not your heart be troubled, neither let it be afraid.” 
John 14:27

“These things I have spoken to you, that My joy may remain in you, and that your joy may be full.”  John 15:11

Let us, with the Psalmist, sing to our Lord Christ Jesus with hearts filled with joy and thanksgiving,
“I give thanks to you, O Lord God, with my whole heart,
 And I will glorify Your name forevermore.”  Psalm 86:12

“Jesus, thou joy of loving hearts,
 Thou fount of life, thou light of men,
 From best bliss that earth imparts
 We turn unfilled to thee again.”
(This in the first verse of an ancient hymn by Bernard of Clairvaux 1090-1153)