what do you mean by day off.
Yes, a partial-day of rest (usually Friday or Sunday*) is good in the week. (*n.b. if you are religious this should correspond with the respective day for you)
Of course it's fine to have days off. I would never see myself being able to study everyday. Your body and mind need some down time. Go out, play sport, partake in your hobbies. Even if it's only a 'partial-day' per week as dan said; it is fine. Personally, I just had breaks if I felt I wasn't working well/got bored/wanted to have a life.
Days off here and there aren't going to mean the end of the world
Try to avoid them where possible. But if you need one, then obviously take one and just catch up the next day. If you're sick and unrealistically weakened, what can you do about it?
I actually think a break (obviously realistically a whole day may be a bit much), is good once a week; to ensure you
(1) don't go insane
(2) don't burn out.
(3) when you get to the end of HSC, you actually would have some passions in life
For me, I rarely studied on Friday nights, and neither for Sunday evenings/nights.
Wherever necessary - do
Necessary:
- Extremely ill
- Important family situation etc.
- Sport representative
A little cold counts as unnecessary. Getting a severe case of the flu to where you constantly have runny noses and headaches counts as a necessary. (Heck, if it were that bad, get a doctor's certificate if you had an exam that day)