It was the wisest man in the world who wrote:
“Fear God and keep his commandments, for this is the whole duty of man.” (Ecclesiastes 12:13)
Unfortunately, he had to find this out the hard way. Solomon grew up as a wise king, favored by God. In his earliest years Solomon led the people of Israel into very prosperous times, both physically and spiritually. As a result of their prosperity, the people of God got too comfortable and ultimately started drifting away. This drifting especially effected Solomon who shifted his pursuits from God to the pleasures of this world:
“I said in my heart, “Come now, I will test you with pleasure; enjoy yourself.” But behold, this also was vanity.” (Ecclesiastes 2:1)
Solomon records his pursuit of drink, great works, servants, possessions, wealth, singers, and women before concluding that it was all worthless (2:1-11).
There are many today who find themselves on the same journey. For many, their life is consumed with the pursuit of fashion, finances, job growth, likability, hobbies, activity, relevance, men/women, and more. The culture, and even many Christians, spend their time looking for ways to live however they want, free from consequences. They want pleasure without pain, and whether they know it or not, they want happiness without God.
You can pursue happiness without God, but you will find, as Solomon did, that this striving is a worthless endeavor. At the end of the day, true happiness is found in God, in fearing Him and keeping His commandments.