Paul tells us in Philippians 4: 4 to rejoice in the Lord ALWAYS, and he even says it again, rejoice! It is a command, and the word "always" implies just that, ALWAYS! Not just when things are going well and we naturally rejoice, no, we are to exercise joy regardless of the situation. Once again, it is humanly impossible...sigh...
The impossibility of it is mainly because, again, as in with love, we tend to confuse joy with happiness. As I see it, there is a core difference between the two terms. In one word, circumstances: happiness is circumstance-driven while joy is Spirit-driven.
Christ knows what human emotions feel like. For example, He knows how it is impossible for a person to be happy when someone dear dies. Remember, Jesus is fully man and fully God. Remember He wept the loss of his good friend Lazarus and wept as His heart filled with compassion for His friends' sisters' distress. Asking anyone to be happy during life's heart-breaking circumstances is like asking a palm tree to produce apples.
Joy, however, goes beyond happiness. The way I see it, joy doesn't even traverse around the same path as happiness. Joy takes a completely different route. That's how the circumstances are irrelevant, because the road of joy is the road of the Holy Spirit and the only circumstance it depends on is the Holy presence of Christ in us.
In the midst of my season of loss, when each day seems as if I lose one more thing, and the snare of worry entangles my soul, I call in joy. I call in His promise,
Weeping may last through the night, but joy comes with the morning. Psalm 30: 5b
And who comes in the morning? Christ does! Jesus IS the Bright Morning Star! (Revelations 22:16b) Joy depends on His presence, so I call on Him and as He reveals Himself to me, the fruit of joy grows, regardless of the circumstance, regarding of the loss, for after all, I must consider it all loss.
I consider everything a loss because of the surpassing worth of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them garbage, that I may gain Christ. Philippians 3: 8