Sleep is extremely important!during sleep, your brain converts short term memory into long term memory.if you study just before sleeping, you will remember it better..so dont think that sleep makes you forget!
It is ok to stay awake till late..if you are comfortable with it but do not reduce your hours of sleep as this can make you forget things.you can also get up early if you want to..but you should get atleast 7 hours of sleep a day.
If you have exams everyday, one after the other, once you come home from one exam, go to sleep for about an hour.this will freshen you up and you can study well for the next exam.Also, it will allow you to stay up late or wake up early the next day.
When you take study breaks, use them to sleep.take small sleep breaks and do not hesitate to use alarms.
