I'm not certain that anyone should have as primary objective 30 more years anywhere, even at a great gig. Times change rapidly and situations do too. Most don't "retire" completely (don't work at anything) but move to a job that's more conducive to what they want out of a personal life. Develop or hone a skill that you can move to if things turn bad. Two 15 year pensions are usually about the same as one 30 year pension. There are tons of government jobs (state, local, district, education etc) that your skills are transferable. Keep options open. Every job has it's bad days, or weeks, but if you're rationally and reasonably unhappy, identify what's causing that and find another position elsewhere that doesn't have that huge negative. I know it's not easy, but neither is most of life. Especially pay attention to the physical part f this job. If it gets to you, look around.
One example that I can share -- one of our regular rural carriers found a position with school district maintenance, and after a year's probation was making more than as a carrier, with no worry about re-evaluation every six months. Another took classes and studied to be a school bus driver, and now is successful and happy at that job.