Have you tried a Pomodoro? Basically work for 15-20 minutes, then take a five minute break, then repeat. Even if you find yourself being distracted, don't judge; just focus on your work again. Also, try setting times during the day when you'll study. Your brain loves routines.

A walk is great after you've tried studying for a period of time. It actually helps build connections in your brain and make studying easier.

I'll admit I struggle with the same thing even when I'm stable, but I tend to always feel tired, which doesn't help.