This is why usually the information and instruction transmitted over the radio should be transmitted in portions, and complex clearances from the controller should be written down when received.

Too much stress is decreasing performance, however no stress at all causing us to be complacent.
The is somewhere in the middle.

Example 1:
Students are learning good when teacher is not stressing them, but they should know that it will be a test at the end of the course. It's applying an acceptable level of stress to keep students alerted during the lessons.

It is always good to keep some margins of stress before it negatively affecting performance.
Person can perform good on higher levels of stress, but for a very limited time.

Too much stress is decreasing performance, however no stress at all causing us to be complacent.
The is somewhere in the middle.

Example 1:
Students are learning good when teacher is not stressing them, but they should know that it will be a test at the end of the course. It's applying an acceptable level of stress to keep students alerted during the lessons.

It is always good to keep some margins of stress before it negatively affecting performance.
Person can perform good on higher levels of stress, but for a very limited time.