תהילים ל:ז פירוש: רש״י

And I said in my tranquility In my tranquility, I thought that I would never falter. However, the matter is not in my power, but in the power of the Holy One, blessed be He. With His will, He set up my mountain, my greatness to be [my] mightbut when He hid His countenance from me, I was immediately frightened.