I have linked three informative articles from @TabataTimes (with a sampling of excerpts from other websites). These serve as a good place to start learning about overtraining and central nervous system (CNS) fatigue. The ultimate take-home from these should be to listen to AND respect your own body.
“Higher training volume, intensity, and frequency are the usual protocols for many who want to get stronger and faster — a principle known as progressive overload. Though it is a widely practiced concept, it can often be done haphazardly and the costs are often overlooked.”
Make sure you are giving your body adequate fuel with which to recover. You also need to be resting enough that stressors don’t exceed recovery time.
Both quality and quantity of sleep are important.
Read, Enjoy, & Please Comment!