When I had a job, being let off an hour early would have thrown me off because I was a janitor and had a specific order and amount of time for each task (half an hour cleaning the bathrooms, then half an hour emptying the trash cans, then one hour sweeping the floors, etc.). Leaving an hour early would have meant I had an hour less in which to get everything done, and I would've felt rushed.
However, I don't consider myself to need that rigid of structure. If someone interrupts a routine like that, it throws me off, but I don't need every single minute of the day planned or anything. I just need to have some idea of what's going on. If I was told at the beginning of the day that I could leave an hour early and I was performing a less routine-based job, I would probably be happy. If I was told an hour before my shift ended that I could go home, it would throw me off because I would've already had another hour of work planned out.
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Yet in my new wildness and freedom I almost welcome the bitterness of alienage. For although nepenthe has calmed me, I know always that I am an outsider; a stranger in this century and among those who are still men.
-H. P. Lovecraft, "The Outsider"