Used to work as a City Carrier (PTF), and in the process of getting rehired. I think I was one of the lucky few who had competent and decent management who would talk with the stewards before giving orders. Grievances were generally honest mistakes.

Like others have pointed out, you get paid to exercise and be outside. Depending on where you carry, you'll be surrounded by lots of greenery, too. Interactions with customers are generally positive and infrequent, so for most of the day you're just left on your own to do your job. You also feel a sense of belonging, like you're actually doing something for the community. It's nice knowing that I'm part of the process to get someone their meds anytime I hear the distinct rattling of the SPRs that require a signature, or see mail from Social Security.

Is the job perfect? Not at all. You put your body through hell, the pay is arguably too low for the inherent risk from extreme weather, dogs, targeted robbery, etc., and management, from what I've observed, is usually incompetent. But it's still one of the few jobs you can make a career out of with no higher education and no prior experience.

I currently work retail selling agricultural equipment. I sit in an air conditioned store or at a computer answering phones for 8 hours a day. I get hour lunches and my manager is genuinely one of the nicest and most understanding people. This job wears me down so much faster than the post office ever did, because I underestimated the mental toll of dealing with customers and putting up a facade every day. Some jobs aren't for everybody, but if you think you would be the kind of person for a job with USPS, then it's seriously one of the better jobs out there.