David Rocks in Your Brain at Work makes a mention of the inverted U plot of performance vs Arousal.
This means stress/arousal should reach a perfect balance to trigger great mental performance of the brain.Anything more than this threshold proves detrimental causing burn out due to over stress.
The neural circuit of the prefrontal cortex of our brain fires absolutely perfect when there is an appropriate combination of two neural chemicals i.e. dopamine & noradrenaline.
By training our minds in the right manner it is indeed possible to generate the right amount of these chemical for optimal brain performance.