Lassitude (noun)
– a condition characterized by lack of interest, energy, or spirit
– a state of physical or mental weariness

Taken from Nella Larsen’s “Quicksand”

“Days, weeks, passed; outwardly serene; inwardly tumultuous. Helga met Dr. Anderson at the social affairs to which often they were both asked. Sometimes she danced with him, always in perfect silence. She couldn’t, she absolutely couldn’t, speak a word to him when they were thus alone together, for at such times lassitude encompassed her; the emotion which had gripped her retreated, leaving a strange tranquility, troubled only by a soft stir of desire.”

The word lassitude on this text was used by Nella Larsen to convey the muddled feeling of Helga Crane towards Dr. Anderson after their sudden that had transpired right at the end of chapter eighteen. Helga’s perception of Dr. Anderson became even more complicated that she doesn’t know how to perceive the situations when they are alone together within the text. Because of this, I’ve come to understand at this moment that Helga is in fact attracted and maybe even in love with Dr. Andersen because of her actions.

source:
https://www.merriam-webster.com/dictionary/lassitude
New Oxford American Dictionary