I did everything. I bought insoles for my shoes, kept my posture straight, I madesure my knees didn't lock and used mats to stand on. I even work out to keep my muscles strong.
Even with that, by the end of my shift, my legs are so weak and tired that I can barely walk and my legs ache the next day. Everyone else just complains of sore feet, but my pain extends beyond that.
Don't say “find a job where you don't have to stand”. I want to make sure I can physically last long enough to find another job, and I don't think I can.