Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.' (Mark 12:30 NIV)
Over time, I learned that the New Testament was originally written in Greek. This helped me because I found out that the Greek language of that time actually had four different words for love. Eros, the word for romantic love (like with my wife), was never used in the New Testament - not at all. So, I don't need to love God in a romantic way. (That's a relief.) Storge, the natural affection a parent would have for a child (for instance), is not used either.
The two Greek words that are used in the Bible are phileo, where we get the word Philadelphia (the city of brotherly love), and agape, a self-sacrificing love where we care about the interest of the other. When Jesus quoted the Old Testament command to Love God, he used the Greek word agapao - love God by caring what is in His best interest, knowing that He already loves us and cares about our best interest.
Whoever does not love does not know God, because God is love. This is how God showed his love among us: He sent his one and only Son into the world that we might live through him. This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins. (1 John 4:8-10 NIV)
You're going through tough times? He loves you and wants to help. You've turned away from Him? He loves you and will even lay down His life to get you back. He loves us first. He loves us perfectly. Our response can be nothing less than to love Him back.
We love because he first loved us. (1 John 4:19 NIV)