Dedicate time off. For me, that meant one day off per week and evenings were no study zones. I did not study during a single evening the entire year, even the day before a hard exam.
Never sacrifice sleep. Giving up sleep to study more is the stupidest thing you can do as a student. Stop.
Constrain your working hours. Don’t try to work more hours, in the hopes you’ll be able to focus. Work in smaller, more intense chunks and you’ll greatly increase your productivity.