There are, of course, many facets to the greatness of G-d, for G-d is infinitely great in an infinite number of ways. The most comprehensive aspect of His greatness, however, is the absolute nature of His existence.
The fact that G-d created and continues to create the universe places the nature of His existence in direct contrast with that of everything else that exists. For whereas everything else owes its existence to G-d, G-d's existence is intrinsic, that is, not dependent on anything else. This means that although other things do indeed exist, their existence is not their own; their continued existence is dependent on G-d and subject to His desire that they exist.
In terms of absolute reality, then, only G-d really exists. As it is written, there is nothing beside Him. Everything else is part of a relative or dependent reality. If G-d were to stop willing some aspect of reality into existence, it would instantaneously cease to exist. Everything other than G-d is essentially nothing; He is the only true something.
The first logical conclusion of this train of thinking is that nothing other than G-d Himself is a worthy object of our fear, for why fear a creature when whatever power it possesses over us is due to the Divine energy within it? And indeed, one of the cornerstones of the philosophy of Hassidism is that a person should fear nothing other than G-d Himself. (The Ba'al Shem Tov was orphaned from his father Rabbi Eliezer as a young child. His father's last words to him were:Yisraelik, fear nothing and no one other than G-d Himself! ) The relationship between a person's awareness of G-d's absolute existence and his fear of anything is thus inverse in nature: the more he is overtaken by the awe of G-d, the less autonomy he will ascribe to any of His creatures or the cause-and-effect workings of nature, and thus the less he will fear these.
In addition, nothing other than G-d is worthy of our esteem, including the most exalted of G-d's creations, man. The absolute nature of G-d's existence implies the insignificance of man in comparison. If a person dwells on G-d's absolute infinity sufficiently, he will eventually feel his own existence palpably shrink into nothingness in the face of G-d's absolute reality. Without focusing on it directly, he will have delivered a fatal blow to his own ego. And having thus abnegated his ego, his worries suffer a similar loss of magnitude: if he is nothing, his problems are surely also nothing.
The feeling of lowliness engendered by this type of thinking does not involve any negative lowering of the individual's self-image. Attacking the ego by dwelling directly on faults and shortcomings is in fact counterproductive since it generally leads to depression or gloom, which serve in the end only to inflate the ego. Rather, the lowliness a person should seek to cultivate is an existential one, that is, a natural conclusion drawn from his awareness of the nature of his existence which, of course, is just the way things are, not any fault of his own. G-d is infinite and man is finite, and even the largest finite number imaginable is nothing compared to infinity.