http://www.sagepub.com/upm-data/44175_2.pdf
Just look up stress response theory.

There are actual biochemical responses that take place in the body, to varying degrees, that can make MG worse. Or anyone's state of health really.
What's ironic about MG is that muscles can cramp up and even more so at night when we're weaker. The more they do, the weaker you get! That hardly seems fair.
Annie