Is anyone else productive one day and completely wiped out for the next 1-3 days?

I'm in university which means the majority of my studying should happen outside of class. Unfortunately I'm in this pattern where I'll get a day where I'm feeling good, motivated, etc but then the next few days are completely lost.

This would make sense if on that productive day I was studying 10 hours or something, but no, it's more like 4? My grades are bad and I can't continue this. Any advice? I know consistency matters but I've never been able to get there haha