The body is a great machine. However, like all machines the body has to take an occasional break. Training every day for months on end, is not productive. It is important to give the body a break to allow for the cells, nervous system, endocrine system and brain to be restored, repaired, and recharged. Training with high intensity day after day, week after week will eventually dull the neural machinery of the cell causing a weak synapse of the neuromuscular junction. The result is that the neural drive will not be as strong and the myofibrils won't contract as hard. Also, the blood volume will be decreased into the area lessoning "pumped up" effect that you are accustomed to achieving with intense training. Your muscles will feel tired and you won't be able to lift as much weight. You might even feel sore and lethargic after workouts during the recovery phase. When this occurs the body is over trained and a break is necessary to re-establish cellular and neural pathways.
Many people feel that if they take time off form training that they will lose all of their hard earned gains. This is not true, in fact, it is best to take occasional breaks to grow more. Though during the initial time off the muscle might feel softer and appear to be smaller, they will get a tremendous surge of blood and greater contractibility when you return to training. This increase in renewed energy will improve the intensity and allow the muscle to produce greater contractions. Stronger contractions allows for more fiber recruitment. More fiber recruitment equals more hypertrophy, therefore greater increases in strength and muscle size can result.
Taking a week off from training is hard on the ego for some people. But they must get past the idea of losing gains. This is an insecurity issue and it is important to leave your ego at the door and realize that taking some time off is actually more beneficial for your body and your training than if you continue to burn yourself out over training.
So go on a vacation and relax, fish, hang out by the pool, and chill with the family. When you come back, you will feel more energetic and tear it up again in the weight room.
Be kind to your body and allow it to recuperate and relax.
Source: Daryl Conant, M.Ed