1Thessalonians 5:14-22 ESV - 14 And we urge you, brothers, admonish the idle, encourage the fainthearted, help the weak, be patient with them all. 15 See that no one repays anyone evil for evil, but always seek to do good to one another and to everyone. 16 Rejoice always, 17 pray without ceasing, 18 give thanks in all circumstances; for this is the will of God in Christ Jesus for you. 19 Do not quench the Spirit. 20 Do not despise prophecies, 21 but test everything; hold fast what is good. 22 Abstain from every form of evil.
Following are a few quotes from C.H. Spurgeon sermon given on May 23, 1886 at the Metropolitan Tabernacle, entitled “Rejoice Evermore”
“The command to rejoice is set in the midst of duties–it is put there to teach us how to perform them all.”
“The joy which God commands is a joy in which it is impossible to go too far. It is a heavenly joy, based upon things which will last forever, or else we could not be bid to “rejoice evermore.”
“We like excitement of a proper kind and we covet earnestly a high and holy joy, but if our rejoicing does not come out of a clear understanding of the things of God and if there is no Truth of God at the bottom of it, what does it profit us?”
“The joy that can always be with us is a part of ourselves–a power of the new nature which God works in us by His own Spirit. . .a full conviction that whatever God does is right. . .and, consequently, a quietness, a calm, a stillness of soul, ‘the peace of God which passes all understanding.’ “
This is just a small taste of the richness of this sermon. Spurgeon cites reasons for rejoicing and objects of rejoicing as well https://www.spurgeon.org/resource-library/sermons/rejoice-evermore/
Lord,
Rejoicing is for my good. You are a good God, and You command what is good for me.
Psalm 119:92-93 ESV – 92 If your law had not been my delight, I would have perished in my affliction. 93 I will never forget your precepts, for by them you have given me life.
Plea for Grace 
Rejoicing. . .