Karamazov is just such a two-sided nature, fluctuating between two extremes, that even when moved by the most violent craving for riotous gayety, he can pull himself up, if something strikes him on the other side.
There are no more uses of "fluctuate" in the book.
Show samples from other sources
Cattle markets tend to fluctuate a lot, and some years, you don’t make much of anything.
Nicholas Sparks -- The Longest Ride
My courage and my resolution is firm; but my hopes fluctuate, and my spirits are often depressed.