Here is some simple advice from what I have experienced in my career of 25 years.
#1- if you make it common knowledge that you have a situation, appointment, gathering, or other important item that you need off for, someone either management or employee will use that info to cause you to worry more whether you will be granted it off. Management likes to not sign slips more when you have a very important publicly known reason attached to it. It's a passive aggressive mental game of torture. Turn in your leave slips as soon as you can without all the explanation as to why you want it off. No ones business. Just creates drama. I have seen fellow carriers heads messed with by fellow employees, and mgt regarding things such as their children's weddings, graduations, and major events in their lives by someone who thinks they hold the upper hand when they really don't.
#2- don't discuss another job that you have during your time outside of the PO. If the job is not during the hours you work at the PO, keep it to yourself. Of course your first priority if there is a conflict is to the PO, but the minute mgt. realizes that you have something job related in your life that THEY CANT control, they do everything in their power to begin to unravel it. This happens. Anything from knowing what your other schedule is will entice postal mgt to deliberately screw with you. I had a second job that was no conflict, but postmaster deliberately moved my start time two hours back in the morning( aux route at the time ), just to interfere with this job, claiming "operational reasons" when I fought it. Had I never discussed my second job, or the exact times I needed to be at it, this would have probably never happened. Keep all of your personal life details to yourself. Good luck