I often studied 14-16 hour days for a solid year when doing my final exams in Oxford University. These are the things that kept me sane, happy, and motivated. You can do this. You already have the ability within you because you are asking this question. With these tips you will be unstoppable.
Relax Every Day - This is important. You have to switch off your mind at the end of the day for your own sanity. Relaxation time is important because that is the time where your mind consolidates all the information you fed it during the day. Protect 'You Time' and give yourself at least 2 hours to relax. Go see friends, talk with your family, watch a movie, read a book, take a hot bath (or contrast shower). Do whatever you need to do to feel normal again. Doing social stuff is a great idea because you don't want to spend too much time in your head.
Keep a To-Do List and Diary - Every Sunday, write out what you will do over the week. And every day before bed, write out and review what you will do the next day. Then tick off everything as you do it. This will give you a little burst of motivation and happiness because you will feel a sense of achievement every day. Write on paper. There is something therapeutic about getting away from a computer screen and organising your thoughts.
Good luck to you! You can do it! Focus on the present, look after yourself, do everything you can, and you will be fine!