I am still poking around different portions that mention joy. At the moment, I have not been seeing anything new.
There does seem to be two primary bases for joy. One is our relationship with God. Two is acting in agreement with our God-designed natures.
Relationship, as we tend to use the word and concept today, is defined rather simply. It involves talking and hanging out. Relationships go far beyond that. It involves actions for and against, offense and forgiveness, judgment, restoration, comfort, presence,and yes communication of all sorts: teaching, explaining, joking, consoling, reproving, warning, etc.
One of the reasons God gives commands is so we know how to live. Obedience to these commands does not follow some arbitrary group of rules. The command follow a design. They either make life more efficient, effective and full, or they enhance our relationships with God and people. That's why the Bible speaks so much about obedience.
And mission is another part of design. It is also part of relationship. Working as a team to achieve an over-arching goal builds relationships. It builds a common mind-set. And in the case of people teaming up with God, it develops God's mind-set in people.