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People commonly say "That's what you're supposed to do"
when they mean "That's what you should do".
People think that the two phrases mean the same thing but they don't.
You remember from grade school English the difference between the active voice and the passive voice.
In the active voice, the subject of your sentence is the one doing the action:
"Betsy the maid made the beds"
In the passive voice, the subject of your sentence is being acted upon:
"The beds were made by Betsy the maid".
When someone says "You are supposed to go to college", it is the passive form of the active sentence "People suppose that you will go to college".
Well, is people supposing that you will do something
a sufficient reason for you to do it? In my world, no.
Of course, if you should go to college, well, you should; if the financial numbers work out and it puts you someplace where you want to be. But going just because people suppose that you will is a bad idea. It could ruin your life.
The point here isn't college, though. The point is be aware of the difference between "supposed to" and "should". They are different.