You'll get used to the feeling, even to the point of being disappointed when you get the OK on an assignment. If you believed that, can I interest you in a nice patch of swampland in Florida? Enjoy the abuse!
And you start reading deep meanings into whether Marilyn sends you the instructor's solution with "Good job!" or with "Good enough!" and a parting nitpick.
Yikes, who let that Jason guy in here?! The deep meaning of "good enough": You left another stupid little mistake in there but this assignment has been sent back so many times I'm just sick of looking at it so just keep it now, OK? Please.