Some people get surprised when they hear how often I train and they wonder if I don't become overtrained of so much training …? Overtraining is when you break down the body's muscles instead of building them up, when the nervous system is at chronically high speed and send out catabolic stress signals to the body. Obviously you don't want to be in that state.
But I think overtraining is rarely what you do in the gym, but more on what you do outside the gym. Because if you train smart and varied, and give your body the rest, recovery and nutrition it needs, you can actually do some kind of workout every day.