The work is very hard. Managers fire people on their whim. Most managers do not have any education behind them and are given to hostile tactics to get their employees to perform faster. While they can not fire the regular employees without a really good reason, they will spend their day making them as misserable as possible until they quit. The job is very dangerous and many of the employees have work injuries or chronic issues related to the physical requirements of the job, or the fact that most postal employees work the graveyard and do not see the light of day. Depression is pretty common.
Sadly management was a bunch of ex military men who yelled and berated there employees. The employees were so miserable and negative. You would work 6 days a week but only get 40 hours, there were not end times you never knew how long you would actually be there. It was hard to get any time off and impossible around any holidays. If I had to pick two words to describe it, it would be life sucking.