How’s my hrs sleep year elevenWatch
Edit: the book "a mind for numbers" covers plenty of aspects on procrastination and you as a student. All memory skills and learning tips can be applied outside of maths/sciences.
Staying awake to the point you are getting tired means your brain isn't working properly so there's no point studying at that time. It's going to take you longer to take in less information cos your brain just isn't running at full capacity.
Absolutely no need to feel guilty for doing one of the main things your body needs. It's like feeling guilty for drinking or pooping cos it takes time from work.