At first glance it would appear that this is like a “carrot and stick” approach to our relationship with God. That is to say, fear serves to deter a person from doing bad, whereas love is an inspiration to do good.
However, I think there are at least two more points to consider regarding “fear” and “love” of God.
One is that these two feelings are actually paired and complementary. Take your relationship with another person for example. If you fear him you will keep your distance. If you love him you will want to draw very near to him. If you both fear and love him you will have a balance of wanting to be very near, but will fear to be too near. This combination of feelings is called “honor” and is the correct approach in our relationship with other people. And so it is true with our relationship with God.
I should also point out that “fear” in Hebrew can also mean “awe” and therefore fear of God is actually a feeling of awe of the great power and knowledge of the Almighty.
The Maharal of Prague, one of the greatest Jewish philosophers, explains “fear of God” in a quite innovative way. He explains that knowing that there is a God who will exact repercussions for our actions is often the motivating factor for our doing what we are supposed to do. This is a “low level of fear”. However, there is a “higher level of fear" that expresses a more “positive” dimension to this feeling. "Fearing God" is not a state of living in fear that I will be punished for my actions — rather the optimal level of fear of God is to reach a point where I am scared that I will do something wrong that will change the balance of God's love for me.
