Jesus tells us the entire Old Testament Law and Prophets are fulfilled in just two commandments (Matthew 22:37-40): Love God with all our heart, soul, and mind and love our neighbor as our self
Now, I can understand the second commandment to love our neighbors as ourselves because our neighbors are very similar to us and the Bible gives us plenty of examples of how we are to love them (I Corinthians 13, Luke 10:25-34, Matthew 25:31-46).
But what does it mean to love God? Pascal, a Christian philosopher, believes that:
God is infinitely beyond our comprehension, since, being indivisible and without limits, he bears no relation to us. We are therefore incapable of knowing either what he is or whether he is.” 
If God is unknowable, how can we have a relationship with, let alone love, God? The answer is Jesus tells us and demonstrates to us who God is. How do we know who Jesus was and that what he tells us about God is true? We know it through two different avenues: the Bible and personal experience.
Knowing about God through a book, the Bible, gives us information but does it enable us to have a relationship with or to love God? Can I have a relationship with Abraham Lincoln by reading a book about him? Can I love Lincoln? I might love what he did but I cannot love him because I do not know him as a person.
Christians say they have a personal relationship with God and Jesus. After all John 16:8 does tell us that the Holy Spirit communicates to us directly and we can pray to God. Also, Christianity teaches that God is somehow involved with each of us on a very personal level (Matthew 10:29-31). However, how do we know what we feel or think about a particular subject is God talking to us or is our personal opinion? How do we sort what God says from the endless chatter of our mind?
God seems to hide himself from us (Isaiah 45:15) or at least we can say that he does not make himself readily apparent. Most everything we know about God we must take on faith. Why does God hide himself? Maybe the purpose of our lives is for us to know who we are. Only when we know who we are can we determine if we have anything in common with God. Only when we know ourselves is it possible to know if we want to have a relationship with God.
 Krailsheimer, A. J., Translator. Pascal: Pensées (Harmondsworth, Middlesex, England: Penguin Books, 1966) p. 150.