Different working patterns work for different people. You need to find the balance that’s right for you while writing your dissertation. It’s a good idea to make sure you are:
Working in a study space that is well-laid out.
Being honest with yourself and the people around you about how you are getting on.
Working and referring to a clear plan for the overall project (with extra time included for anything unforeseen that may pop up).
Eating well, and keeping your alcohol, caffeine, nicotine and sugar intakes under control.
Getting sufficient sleep and exercise.
Balancing your work sensibly, seeing friends and having reasonable relaxation breaks.