This was many years ago, but it was probably one of the first times I realized no employer has your back. I was a temporary worker doing basic file clerk work for the summer. My coworker had back surgery from an injury at a previous job, and wasn't supposed to be lifting over 50 pounds. The totes filled with files that we regularly had to lift could come near that, but rarely went over 30 pounds I would say. I was only 17, so I didn't know any better, but I had a good rapport (so I thought) with my boss and I let it slip (assuming she knew) that he wasn't supposed to be lifting over a certain amount. Looking back, maybe they would have worked with him on it had he told them in writing. Needless to say, they let him go that day.
Companies & corporations (and by extension managers) are not your friends, you're disposable to them.