One of the precepts of successful bodybuilding is to stress the muscles enough by lifting heavy weights to tear down the muscle tissue, thus inducing the body to rebuild the tissue, bigger and stronger than it was before. But the real secret is to give the body enough nutrition, time and sleep to accomplish this. You can work your ass off in the gym, but if you don’t give your body what it needs to recuperate, you’re wasting your time, and you might even lose muscle mass and strength.
There’s also the psychological element involved – if your brain gets burned out you won’t make any progress, either. It’s called overtraining.
The same thing can happen to you when you play too much. I know, because i’ve played 7 nights a week for months at a time and found myself playing worse instead of better. My technique was still intact, but my brain didn’t seem to be functioning at its usual capacity, like – well, what it was, was I seemed to have lost some of my creativity and originality. I was playing the same old things, and boring myself to death with them. The simple fix was to take a few nights off and then I came back better than ever. No big deal. So that might be something to keep in mind if you play a whole lot of gigs.