First off: if you have kids, you will jot really see them more than on your day off. If you're married and its rocky: kiss it goodbye, because if you work for USPS they own you now. IF YOU WANT A SOCIAL LIFE OUTSIDE OF WORK: DO NOT APPLY!!! Seriously, you will have about three hours at home 6 days of the week PERIOD. Overtime is mandatory, and despite what you are told before you are hired, it is all of the time. Not just for the holidays. For the last year I have only had two days off in a week once, and I've been sent home before my 12th hour twice. one day off a week is the usual, but no days off late November through the first week of January, you can't call in sick, no vacation time. Being a Casual means that you are not allowed to be part of the Union. If a Union steward, or member sees you treated poorly they can file a grievance on your behalf if they see fit.
Probation never ends for a Casual: if you look at a supervisor the wrong way they have every right to take your badge and walk you out...fired. If you see other employees taking extra or extended breaks do not do the same!!! They will not be reprimanded but you can and WILL.
There is a bit of segregation between crafts. Clerks tend to hang out with Clerks and Mail Handlers tend to hang out with Mail Handlers. I think it's just because Clerks tend to be more quiet and civilized as where Mail Handlers tend to be louder and kind of crass. There will be cussing, and people will pick on you...hopefully in a friendly kind of way.
Avoid the gossip if you can, and don't sleep with your coworkers, it can be a bit of a melt pse place situation. If you come into work, do your work!!
Love your job because when you arrive for your tour you will be welcomed home...and it's not an exaggeration.