I’m a staunch advocate of regular, disciplined physical training, and in fact I’ve recently increased my own regimen from four days per week to seven.
Yet even with that personal commitment that I have no intention of breaking for the next few months, I still know that sometimes, it’s OK not to train when planned.
Your body is a system of systems, and, while physical training bolsters the performance of the other systems, you must also not stress any one of those systems to the point which it throws the others out of balance.
It’s about finding the right amount of stress each day that you train, not the maximum.
Matt Fried 