In my opinion most workers especially the ones who been there for years will put minimal effort. As long as you show up on time everyday its hard to get fire.

Making you go to other post offices and doing mail routes and you don’t even know the city. Just not mail either your dealing with over 200 packages a day

not being able to get a full time position let alone enough hours before your full time

It depends on the job. As a letter carrier you have to get used to the weather and physical demands. It looks pretty easy to deliver mail but it is not. The demands by management are frequently not reasonable as well. I had good managers and bad managers but the relatively small number of bad managers were really BAD! I was a mail handler also and you have to get used to the boredom. I suggest becoming a retail clerk if possible. No ot for them tho. When you first start they can really work you to much. 6 days a week usually.

Going up and down a lot of stairs had 2 knee replacements

The most challenging is keeping calm and just prepare yourself for very long hrs. And working 6 days a week. Remain professional and document everything.

One of the most challenging parts of working for USPS can be the physically demanding nature of the job, including long hours of walking and lifting heavy packages. However, it can also be a rewarding job with opportunities for growth and stability. If you're looking for job opportunities in addition to USPS, consider checking out Jobcase along with other job search providers for a variety of options.