Musar zu Jeschijahu 63:19

This is because of the dread these lofty angels constantly experience of G-d's exaltedness, blessed be He, lest they detract a small amount from the honor and holiness due before His presence. Whenever and on whatever place the divine presence reveals itself, there is agitation, trembling, and quaking. This is what scripture refers to saying: "The earth trembled, the heavens also dropped at the presence of G-d" (Tehilim 68:9), and "had You rent the heavens, had You descended, mountains would have melted from before You" (Isaiah 63:19).

This is what our sages said: "Know what is above you: an eye that sees, an ear that hears, and all your deeds are inscribed in a book" (Avot 2:1). For since the Holy One, blessed be He, watches over every thing, and He sees everything and hears everything, certainly every action will leave an impression. And all of them are inscribed in a book, whether for merit or for debt (punishment).