There are a few little things that help when studying... I've been in school for something like 8 years (was initially a physics major, had to work full time and switched to history major part-time, and am now back to physics), so I feel like I'm probably a study expert at this point.
- Don't eat any carbs before you study or go to class. Protein, vegetables, and maybe some fruit (but not bananas) if you feel like you need it. It might be that your blood sugar is crashing if you tend to eat carby foods a lot. Same with a lunch break; the only carbs you eat should be at night if you're planning to study all day.
- Listen to music with a beat, but that isn't too complicated. This keeps your brain plugging along with the music. I find that
This Morn Omina is the best math music for me, personally. I'll listen to like 4 or 5 albums by them, look at the clock and am amazed at how much I got done. Don't listen to anything with lyrics to distract you, unless you're okay with listening to another language, since you can't understand it anyway.
- Do NOT cross your legs when you study. This just makes blood pool in your legs, so even if you walk around every 15 minutes you might still be keeping blood from getting to your brain when you're actively studying. Similarly, make sure your posture is good... if you tend to slouch, your neck is going to be at a weird angle and you're restricting blood flow that way, too. This can be hard when you're hunched over a book, but your muscles will get used to it eventually.
- Do you study at home/in your dorm, or do you go to a library or somewhere to do it? Slowly start staying longer and longer at the library, maybe by only 15 mins or so, and it'll train you to believe that "when I'm at the library, it's study time".
- You can also use a trigger, which... I'm not sure how I feel about and don't use it myself, personally. But just like Pavlov's dog, you can use something that tells your brain, with no exceptions, that it's time to study. I've read it more than once where a specific type of stretch and/or breathing exercise is used. You might even be able to start off each study session with the same song, or something like that. I used to listen to a certain song in the wee hours of the morning (just because it turned out that way) and now I associate it with dawn. I can't tell you whether it works for studying, but you can try it when you first start studying and then later when you lose steam. This will take a while to train yourself for, though, and I'm not sure how long it will take.