Yerkes-Dodson Law

At low levels, added stress raises activation: the task becomes urgent enough to command attention and effort. That can increase creativity rather than suppress it. But the effect does not rise indefinitely. Once stress crosses the useful middle range, extra pressure stops acting as stimulation and starts interfering with performance. The cause and the cure are therefore the same variable at different intensities.

The principle identifies a rise, a peak, and a decline; it does not tell you the exact deadline or stress level that will place a particular person or task at the peak. Treating every performance drop as proof of excessive stress would also confuse a suggestive pattern with a complete causal diagnosis.