That's the exact reason they push interns beyond breaking point. My friend regularly made silly, dangerous mistakes when tired - every time he did a serious dressing down ensued.

Because he was an intern a qualified doctor always double checked him so none of the mistakes were enacted. But he learned his limits and how far it was safe to go.

People put their lives in the hands of doctors; they are under pressure, overworked and often have a tiny margin for error. Knowing your limits is one of the most important aspects.

This is the reason usually only the brightest and hardest workers at school make the grade to become a doctor. Not because of their smarts - but because they can concentrate and focus on a task and achieve highly on it in a consistent way, even under pressure.