in each class, get a feel right away for what the actual workload is going to be (in terms of both "what's the bare minimum I can get away with" and "what's required for my Best Possible Work"), what kind of flexibility which instructors will give you (is one gonna flunk you if your assignments aren't in On The Dot or give you grief if you aren't Visibly On Camera Taking Notes the whole class?), and where you can take shortcuts without significant detriment (ie. a lot of classes I took would assign reading, but then cover the content of the reading in the next class's lecture, so I got by just skimming the assigned reading and spending that time on more important, time-intensive work).
basically, just accept that you don't have a workload like that and give each thing 110% the whole time, and figure out how to balance the Actual Needs of each class so you can complete those while still respecting your time and care for yourself.