Stress
Did we mention that people skills are really, really important for librarians? They are. But even those with the most stellar of skills can't escape the stress of dealing with often-frustrated library patrons.
There will be wild-goose-chase research projects—"Why is there air here and not there?"—that have no solution, never had, and never will. And you'll get blamed if you come up with nothing, nada, zilch.
Don't even get us started on library fines. The source of the highest decibels in library land is the voice of an angry patron, screaming that he shouldn't be charged a cent for a book that "forgot" to return itself for two weeks.
Things like that. We suggest practicing the "smile and nod" technique.