Sentence:  Then I was forced to rest; and, sitting down on the ground, saw that the glimmering streak of light had faded, and that the awful blackness of the previous night was creeping up again. And now I had no heart to face it, being cowed with hunger, thirst, and weariness; and so flung myself upon my face, that I might not see how dark it was, and groaned for very <WSD>lowness</WSD> of spirit. 
Meaning of the word marked with <WSD> tags:  The property of being low.