How do you experience joy?
Chances are that you can identify some activities, memories, or experiences that made you feel joy. Things like connecting with nature in all her splendor and getting away from the fixings of our modern lives, being in the company of people you love, or doing an activity that warms your heart, are examples. What you identified is likely joy that was created by an external source. While these experiences are important in our lives, the tradition of yoga teaches that if we grow attached to them (raga) or conversely avoid or dislike other experiences (dwesha), we set the stage for suffering - wanting more of this, avoiding that.