As Robotcops says in his or her inimitable style, you have to organise your work, rest, and play. Treat studying as your job. As with a job, plan your day, and be sure to take time off for eating, exercising, socialising, and sleeping.
Learn how to speed-read a case, article, or book. Use the ICLR law reports. Those are in any event the ones which Courts prefer lawyers to cite, so using those reports above others is a good habit to acquire if you intend to practise law. The headnotes in ICLR reports identify the key passages in each judgment.
Practitioner textbooks are a secret weapon for law students. They are less discursive than student textbooks, and they have very clear tables of contents. For example, Chitty on Contracts is way easier to find answers in than any student book on the law of contract.
Do not fret if you don't read everything on a reading list. Aim to read about three quarters of the material if you can. Tutors may guide you on which items are more important than others. If a tutor specifically mentions something on a list, be sure to read that.
You should find that your capacity for work increases year on year. Bear in mind that the workload at university is light compared to the workload in legal practice, so if you after trying to assimilate to the workload you still don't like it, that's life telling you not to become a lawyer!