Anyone sooner or later, for one reason or another (not only athletes), will experience some form of overreaching or overtraining.
Overreaching is a more common situation as it comprises, for example, strenuous training sessions without adequate recovery. This is highly preventable and "curable" as it may mean a bit more rest days or simply reduced training load/intensity.
Overtraining, on the other side, is a far more complicated matter. It is a syndrome with in some cases even clinically relevant biomarkers.