John 15:5

I am the Vine; you are the branches. The one who remains in Me and I in him bears much fruit, for apart from Me (that is cut off from the vital union with Me) you can do nothing. 

In the pursuit of happiness, life without Jesus is unfulfilling. The problem is understanding the purpose of life if there is no God in it. The goal is not self-satisfaction only; when that is realized after meeting a goal and still being unhappy, people wonder what life is for. We cannot live a fruitful, purposeful life apart from God. God has designed us with a purpose; without Him, we will never realize it.