You've heard that expression.  You might even call yourself "God fearing".

Basically it seems to mean that one is upright, living life as he or she would believe God would want.  

Sometimes you might think that means somebody should tremble in fear before the Almighty..fear the omnipotent one. But, we should realize that a benevolent God, the same one that his Son, our Lord Jesus Christ spoke of, when he taught  us how to pray with, "Our Father which art in heaven.."  This God would not be one that would cause us to tremble in fear.

Now, Paul makes it clear that he trembled in fear before the radiant face of Jesus Christ. He did so, I believe because of the sudden shock of the event and, because he was persecuting the followers of Jesus, that he would be punished.

Of course he was..he was made blind, but this was the Christ's way of showing Paul that he was blind to the truth. 

 But we were talking about fearing God.

A definition that I prefer can be found in Proverbs where we  read "To fear God is to hate evil".  That pretty much says it all..bobnPaul