I used to have a problem with the idea of fearing God. What's fear got to do with loving God? Why would God want to instill such an unpleasant emotion in us if He was truly Loving and Merciful?
Then I was reminded of the time I saw a mother yelling at her 6 year old son for racing up and down a flight of stairs with his friend. She warned him once with a stern voice. It didn't work. Eventually she walked over to the stairs, yelled at him and pulled him aside for putting his friend and himself in danger. She instilled fear in him.
She did it out of love. And he knew that. So he stopped.