In chapter 7 What ahead seemed to have caused westerberg's bad attitude?

Westerberg's bad attitude was caused by exhaustion from long hours at work, and a lack of help at the grain elevator.

An hour later he emerges, smeared with grease and chaff but successful. “Sorry about snapping like that,” Westerberg apologizes. “We’ve been working too many eighteen-hour days. I guess I’m getting a little snarly, it being so late in the season and all, and us being shorthanded besides. We was counting on Alex being back at work by now.”