I screwed up a deadline for grad school, actually I screwed up a few deadlines. First, if you live on the East Coast, your course calendar of midnight deadlines on Midwest time may appear as due the next day. And then you’ll hand in every thing a day late for, like, weeks before realizing you’re not doing B work, you’re getting dinged for late submission every time.
At the beginning of last session, I didn’t allow enough time to pick my classes and I wasn’t completely delighted with the courses I ended up with, so I set a calendar alert for next session’s registration. This way, I’d have plenty of time to browse reading lists, see what my teachers have published and scroll RateMyProfessor, and still have time to enroll before classes are full. I don’t know if the school schedule changed, if I confused pre-reg and add/drop, or if I just entered the wrong date, but when my GCal alert popped up, it was not the day before pre-reg opened, but just a couple of hours before pre-reg closed. So that wasn’t awesome.
As an undergrad, I registered for basically every class at the last possible minute, and that turned out ok. And this will turn out just fine too, since the options in my program are all pretty good, but I was really trying to do better than fine. It is so much worse to screw up after actually trying to be organized.