As the reality of Yukon travel becomes too harsh to bear

I'm sorry, you haven't posted a question in your post. The following quote is the closest explanation for the information you've provided.

By this time all the amenities and gentlenesses of the Southland had fallen away from the three people. Shorn of its glamour and romance, Arctic travel became to them a reality too harsh for their manhood and womanhood. Mercedes ceased weeping over the dogs, being too occupied with weeping over herself and with quarrelling with her husband and brother. To quarrel was the one thing they were never too weary to do. Their irritability arose out of their misery, increased with it, doubled upon it, outdistanced it. The wonderful patience of the trail which comes to men who toil hard and suffer sore, and remain sweet of speech and kindly, did not come to these two men and the woman. They had no inkling of such a patience. They were stiff and in pain; their muscles ached, their bones ached, their very hearts ached; and because of this they became sharp of speech, and hard words were first on their lips in the morning and last at night.