"Overtraining is real, but it is very misunderstood and grossly overstated by most people. 99% of people will never experience overtraining, and maybe only 5-10% of athletes. Now, fatigue is common and a normal response to training. For full blown overtraining to occur that fatigue would have to accumulate over a period of months. Most people will take a few days off, or an overuse injury limits their training, before overtraining develops."