Life is short... and it's not about us. Eternity is long... and it's all about God.
When God made the universe, he intended that everything in it would point praise back at Him. Every glittering star, every speck of sand, every ocean wave, every strand of DNA—everything was designed to declare how great God is. Even in making humanity, God really wasn't too concerned about us; he was thinking mostly about Himself. God was focused on how we would magnify and glorify Him (see Isaiah 43:7).
God is most concerned about Himself. In essence, God approaches every decision with this question: "What would bring me the most glory and honor and what would make me look the best in this situation?" Then he acts accordingly.
God declares, "I am the Lord; that is my name! I will not give my glory to another or my praise to idols" (Isaiah 42:8). God made everything, and He made all of it to give glory to Himself.
We far too easily forget the truth that this entire universe is about God, and instead we try to hijack the spotlight to focus on us. We spend our short, little 60, 70, or 80 years here on Earth trying to make much of us, forgetting that all of creation is designed to make much of God.
God made you for a purpose, and He sent Jesus Christ into this world to invite you to join His purpose for your life, which is to magnify His name. So, don't waste your life magnifying something that is like a wisp of vapor or a puff of smoke, which is visible for a little while and then disappears into thin air. Instead, leverage your life as part of the eternal story of God—a story in which every second lifts up and magnifies God.
JOY comes by putting Jesus first, Others second, and Yourself last.
Everyone wants to enjoy life. Many people place the source of their joy in what they own, in their reputation, in their status, or in other worldly things. Yet, all of those things are unstable and can easily evaporate, taking joy with them. In the end, we will depart this world just as we entered it--with nothing (Ecclesiastes 5:15). So, although all of these sensual pleasures may provide short-term happiness, they clearly fail to provide genuine, lasting joy (Ecclesiastes 2:10-11).
On the other hand, true joy is offered in Christ. In John 10:10, Jesus said, "The thief comes only to steal and kill and destroy; I have come that they may have life, and have it to the full." Living life to the full includes living it overflowing with joy.
In Luke 4:18-19, Jesus quoted the first few verses of Isaiah 61 and applied it to Himself. In Isaiah 61:3, that quote continues by saying that he (in this case, Jesus) came to provide for those who grieve in Zion -- to bestow on them a crown of beauty instead of ashes, the oil of gladness instead of mourning, and a garment of praise instead of a spirit of despair.
One of the side effects of Jesus coming to Earth was that we could have lasting joy. Indeed, the gladness and joy that so many people so desperately want can be found only in Jesus.