Descartes Stated, " I think, therefore I exist". 

Romans Chanpter 2 vs 19 - State, "since what may be known about God is plain to them because God has made it Clear to them"

Everyone knows that they exist and also that God Exists. 

The current culture we are living in is self centered.  It is about us and what we want to do and accomplish.  We know God exists, but we do not put God front and center in our lives. We create our own morality rules where everyone's is different.  Due to this we will not succeed in accomplishing happiness.  Each persons perceptions are different leading to conflcts and misunderstanting.  We know God exists,  He has given us one set of rules, which we should follow, but because of our sinfulness we will never perfectly accomplish them, but through Jesus dying, our sins are for given.  We need to focus on the one true God and put our trust in his Word and ask for forgiveness.  This is the only way to true happiness and everlasting life.