Rabban Yochanan ben Zakkai told his pupils that he hoped they would experience fear of Heaven in the same way they experienced fear of man.
That is, the experience should be vivid physically, emotionally, and intellectually.
It is not just a deep inner conviction but something that compels appropriate action.
One cannot fear God as a witness, as one who merely looks on.
One fears God because one feels Him, both within oneself and without.
He is “here,” and my life as a whole reacts accordingly.
–Rabbi Adin Steinsaltz