Just because you’re told to practice hard it doesn’t mean that you won’t even take breaks. Is very important that you have period of rest between your activities. Not only because it would give you more energy, has it had also other benefits. It makes practicing less tiring and less boring; it helps you prevent the risks of having injuries, and also gives the mine more time to process information. But that doesn’t end on that.
Most people have already experienced the benefits without even realizing it. For example, you’re practicing guitar real hard for the whole day, and then you have to go out for something. When you come back you noticed that your guitar playing is a more better and has improved. You might not notice it but that is one benefit of rest. Especially on work, it is not good to work straight. Should take a break once in awhile; get yourself a nap for 20 minutes and that would be enough to recharge your body and mind and would give you power to move on further rest of the day. This is a proven fact. So whenever your practicing hard the whole week, give yourself a well deserved break and you would notice good results.