I think the top of this list is making sure that I'm exercising regularly, eating balanced meals, and getting enough sleep. This helps set me up for success with studying - I'm less restless, it's easier to focus and process information -- and all of that together helps me feel less demotivated when I hit a roadblock.
In terms of tools - meds for sure, having snacks and water at my desk so I don't need to get up, I also have visual timer on my desk - so I can visibly see how much time I've spent studying (or being distracted lol)
before I start studying, I try to (but honestly need to get better at) setting reasonable goals -- listing out what I need to do, describe the steps it will take to get the task done, write out how long it will take (v helpful with time blindness), and choose what I will be doing during that study session.
If I feel overwhelmed/stressed/dont want to do all of that, I have flashcards that I go through instead -- I used to use anki but i've switched over to remnote and i've been enjoying that so far
sometimes I'll put on some binueral beats (which I typically describe as pseudoscience that works) -- and i think the noise just helps stim my brain a little bit or sometimes the noise just reminds me that I should be working.
and don't forget that we're prone to hyper focusing! it's not sustainable to work for 6 hours straight without getting up, eating, drinking water - those sprints might feel good but we end up feeling exhausted from them the next day.