There’s not much addo about the releationship of men and their penises. For most men a penis can only have two states:
ON and OFF.
There’s no need for another one. But this is not the whole story. Men barely talk about this. Welcome to a secret:
Ok, for sure there’s a pure physical explanation for this occurence. But can’t you hear John Mayer’s penis say:
“John! This time it’s personal!”