Breaks are short enough that your mind doesn't wander too far and often enough, to not feel like a break is still 4 hours away.
The benefit of this is that it turns the whole process into a habit. It's not about today or tomorrow, but rather about the 2-3 weeks that you spent studying. This helps me with feeling positive about the progress I made (even if it's small).
Some things that help me:
- Reminding myself that I took those 8 hours for myself (to get things done)
- Having a deadline (exams) allows me to schedule topics (set expectations low)
- I don't have any apps to doomscroll (twitter, facebook, instagram), so a 5 minute break is plenty to respond to a friend
- Most of my breaks are not spent on my phone (getting water, fresh air, walking around house, stretching, talking to people)