Believe it or not, joy and happiness are not the same thing. Clever though it was, don't allow the Pixar film to confuse ya, folks.
Joy isn't some emotion that dominates you whenever "she decides to exert herself." And joy's existence at any given moment is neither dependent on your current circumstances nor on how you presently feel.
Rather, joy is like the sun; while its visibility to our world changes with the climate of emotion, it is always there. Joy is rooted in the truth; we do not lose faith in this "sun's" return because of its constancy.
Happiness, on the other hand, is rooted in the situational illusion of our current "weather conditions." When dark, brooding clouds block the sun from our view, we declare, "No sun today," thus replacing this "sunny" weather condition with a "stormy" one. Happiness is fleeting and temporary, and as long as we continue to pursue it, we will find ourselves reigned by the rain of despair.
So if the quest for happiness is merely a vicious cycle, where can one seek joy? The answer is: like the sun, joy dwells far beyond earthly matters. Although the earth provides glimpses of the sun's full brilliance, these glimpses are, in themselves, limited by the extent to which the earth's conditions interfere.
Notice the wording of these lyrics you have probably been hearing recently: "Joy to the world." It doesn't say joy of the world, but rather, joy to the world...
Joy to the world, for in spite of our foolish rejection towards the Source of our energy; in spite of our resistance towards What we, in our nature, revolve around, His love overcame our obstinance.
"He was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was on him, and by his wounds we are healed." -Isaiah 53:5
Joy to the world because the Son has come in the midst of our self-inflicted chaos to enlighten Earth with the Truth.
"For this purpose I was born and for this purpose I have come into the world—to bear witness to the truth. Everyone who is of the truth listens to my voice.” - John 18:37
Joy to the world because through Him, we needn't even fear death... His death has allowed us to live out our destiny, which is not to find glory before death— but after, for we were created for eternal life.
"He will wipe every tear from their eyes. There will be no more death or mourning or crying or pain, for the old order of things has passed away.” Revelation 21:4
"O death, where is your victory? O death, where is your sting?"- 1 Corinthians 15:55
Joy to the world because if we live for Him, we no longer have to live for this broken world; the circumstances of this life are no longer fatal, but instead, hold potential for His triumph.
"I have said these things to you, that in me you may have peace. In the world you will have tribulation. But take heart; I have overcome the world.” - John 16:33
"But seek first the kingdom of God and his righteousness, and all these things will be added to you. Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own." - Matthew 6:33-34
"Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day. For our light and momentary troubles are achieving for us an eternal glory that far outweighs them all. So we fix our eyes not on what is seen, but on what is unseen, since what is seen is temporary, but what is unseen is eternal." - 2 Corinthians 4:16-18
Above all, Joy to the world because through Jesus Christ's loving sacrifice, our union with God has been restored; He always abides with us, even when our world makes it seem otherwise:
"Even though I walk through the darkest valley, I will fear no evil, for you are with me; your rod and your staff, they comfort me." - Psalm 23:4
"Where shall I go from your Spirit? Or where shall I flee from your presence? If I ascend to heaven, you are there! If I make my bed in Sheol, you are there! If I take the wings of the morning and dwell in the uttermost parts of the sea, even there your hand shall lead me, and your right hand shall hold me." Psalm 139:7-10
"Come to me, all who labor and are heavy laden, and I will give you rest. Take my yoke upon you and learn from me, for I am gentle and humble in heart, and you will find rest for your souls. For my yoke is easy and my burden is light.” - Matthew 11:28-30
So no matter how toilsome your suffering may become at times, remember it is only a temporary illusion; joy has not left you! Always recognize the truth that since joy comes from God, who is with us always, it is exists perpetually and constantly. And choose to rejoice, trusting in the Lord's plan for you:
"'For I know the plans I have for you,' declares the Lord, 'plans to prosper you and not to harm you, plansto give you hope and a future.'" - Jeremiah 29:11