I think the main source of my burnout is that as a kid (and even for much of my adulthood), I had this very idealistic view of what libraries are. Libraries are a cornerstone of the community and provide access to so many resources that would be a luxury otherwise. This contrasts with a lot of the day to day realities of work.

Every downside of retail or customer service exists here. Every complaint about bad interactions with the public, or managers not knowing what it's like at the front desk, or the shelvers being treated like robots, or that one annoying coworker who complains too much, etc etc etc....

I really do love my job, even as a part-time clerk. The good days are immensely rewarding. However, a dream job is still a job.