We experience stresses everyday. Waking up is a stressful event.

A man can transmute this sexual energy into purposeful action & drive. Ironically, this tends to make his partner pretty horny.

It's generally when the man can't find a purpose that he experiences the frustration of it. He then seeks to offload this energy & find relief from it. 

 Agree and women do not tend to do the same especially when it comes to sex.