What do athletes and fitness fanatics share in common that can be their greatest asset but also their ultimate downfall?

Perfectionism and obsession. When this leads to over-training. You want to be training more than everyone else. Working harder than everyone else. You put in the hours even when your body is crying out for you to stop. It’s a fine and difficult line. So how do you know when you’re overtraining? How do you know when you’re doing more harm than good?