Should you keep studying or go to sleep?

Answer 1

You should always sleep then your brain and yourself is better to think about it. After a good nights sleep you're more freshed and able to think about anything.

If you are on the verge of sleep while studying, I suggest just going to bed. Then, continue studying in the morning. It's better to have a rested mind that can think clearly, then to try to cram everything while you're tired.